Identification method of interaction region in the internal flow field of thin film evaporator for high viscosity materials

Abstract

The present invention relates to a method for identifying the interaction region in the internal flow field of a thin-film evaporator for high-viscosity materials. The shape of the internal flow field of the thin-film evaporator is a three-dimensional vertical cylindrical tube, and the gap width of the thin-film evaporator is d. The identification method is as follows: (1) Perform meshing on the three-dimensional vertical cylindrical tube; (2) Divide the three-dimensional vertical cylindrical tube; (3) Count the total number B of grid nodes corresponding to the gas-liquid interface i and the total number A of grid nodes of the i-th three-dimensional vertical sub-cylindrical tube i . After calculation, the proportion C of the interface grid nodes of the i-th three-dimensional vertical sub-cylindrical tube is obtained i ; (4) Draw a graph with the abscissa being i or a parameter related to i and the ordinate being C i , and find the interaction region between the liquid mass and the liquid film from the graph. The present invention can accurately obtain the interaction region between the internal liquid film and the liquid mass, and then distinguish the liquid film distribution region and the liquid mass distribution region to complete the structural division of the flow field of the thin-film evaporator

Description

Technical Field

[0001] The present invention belongs to the technical field of thin film evaporation equipment, and relates to a method for identifying the interaction area in the internal flow field of a thin film evaporator for high-viscosity materials. Background Technology

[0002] The scraped film evaporator has an internal structure like Figure 1 As shown in the figure, it is a new type of high-efficiency evaporator that can perform falling film evaporation under vacuum conditions by forcing film formation through a rotating scraper. It has the characteristics of large production capacity, high efficiency, and short material heating time. It is suitable for distillation and concentration in the pharmaceutical, food, chemical and other industries.

[0003] As a new type of high-efficiency evaporator, the scraper thin film evaporator is favored by scholars at home and abroad, and researchers have conducted a lot of research on it. Among them, the flow, distribution and transmission mechanism of the fluid in the scraper film evaporator directly determine the evaporation efficiency and power consumption of the scraper film evaporator, so it has become the focus of research. However, the existing research on the flow field inside the thin film evaporator is based on the internal in-line scraper blade structure (such as Figure 2 ), and at the same time made a lot of simplifications, and obtained the most classic flow field morphology theory (as shown in Figures 3 - 4 shown in Figure 1), this theory simplifies the flow field inside the thin film evaporator into a relatively regular circular wave at the leading edge of the blade 3 and a thin and uniform liquid film scraped out by the trailing edge of the blade, and ignores the changes in the axial flow field shape. Existing studies are based on this model to explore its liquid film thickness characteristics, residence time characteristics, heat and mass transfer characteristics, etc.

[0004] The materials selected in the existing research are mostly Newtonian fluids, and the viscosity is concentrated within 10Pa·s. There are few reports on the simulation of high-viscosity non-Newtonian materials in such evaporators (Numerical simulation of flow field characteristics of non-Newtonian fluids in wiped film evaporators [J]. Acta Physica Sinica, 2022, 71(05): 197-208.). The flow field formed by this kind of Newtonian material with relatively low viscosity in the evaporator is similar to Figure 3 and Figure 4 The flow field shown is approximate, and is far from the actual flow field morphology of high-viscosity non-Newtonian materials in the evaporator. Therefore, it cannot be used as a basis for describing the flow field morphology of high-viscosity non-Newtonian materials in the evaporator and identifying the interaction area.

[0005] When the actual thin film evaporator is used in high viscosity material occasions, in order to promote the high viscosity material to form a good film on the evaporator wall and improve the production capacity, the blade shape on the rotor (such as Figure 5As shown, it is usually very complex. At this time, the flow field inside the evaporator will be different from the form introduced in traditional theories. Its flow pattern becomes complex and diverse. The simulation results are shown in Figure 6. At this time, the liquid film 2 is no longer a uniform and flat film structure, and the shape of the liquid mass 1 is no longer the traditional circular wave, but an irregular shape distributed periodically; moreover, there is a very intense exchange behavior between the mass and the film, manifested as an increase in the contact area between the mass and the film, and large deformations occur in both the mass and the film at the contact positions.

[0006] It can be seen that for the thin-film evaporator for processing high-viscosity materials, it is very difficult to describe the distribution characteristics of its internal flow field through a single axial or radial cross-sectional view, and it is impossible to accurately distinguish which area is the liquid film and which area is the liquid mass. This brings great difficulties to the understanding of the evaporation and dissolution mechanism of such thin-film evaporators, the evaluation of their performance, and subsequent optimization design.

[0007] Determining the interaction area between the liquid mass and the liquid film is the key to distinguishing the liquid film area and the liquid mass area. However, for the internal flow field of the thin-film evaporator for high-viscosity materials, the prior art cannot accurately determine the interaction area between the liquid mass and the liquid film. Summary of the Invention

[0008] The object of the present invention is to solve the problems existing in the prior art and provide a method for identifying the interaction area in the internal flow field of a thin-film evaporator for high-viscosity materials. Specifically, the present invention restores the flow situation inside the evaporator through CFD simulation, and identifies the internal flow field structure based on the simulation results. By processing and analyzing the calculation results of a huge number of grid nodes in the three-dimensional flow field model, the interaction area between the liquid mass and the liquid film is obtained, and then the distribution areas of the liquid film and the liquid mass are obtained, so as to accurately divide the flow state of the flow field. Based on this method, the internal flow field can be effectively analyzed and described quantitatively, which is beneficial to the subsequent optimization design of the structure and process.

[0009] The formation process of the basic concept of the present invention is as follows:

[0010] For the division of the liquid mass and liquid film areas, first, the position of the gas-liquid interface needs to be found. The gas-liquid two-phase distribution cloud map can be used to pick up the gas-liquid interface. For the internal flow field of the thin-film evaporator (a three-dimensional vertical cylindrical barrel, such as Figure 7After meshing the structure (as shown), the volume fraction of each grid node can be determined according to the gas-liquid two-phase distribution cloud map. Since the volume fraction is an important parameter expressing the proportion of gas and liquid phases in the grid node, the type of each grid node (gas phase, liquid phase, gas-liquid interface) can be determined. For example, in the right figure of Fig. 6, the volume fraction of all grid nodes in the red part is 1, indicating that these grid nodes are filled with the liquid phase; the volume fraction of the royal blue part is 0, indicating that all grid nodes in this area are filled with the gas phase; and the transitional color part indicates that there are both gas and liquid phases in these grid nodes, and the volume fraction is between 0 and 1, and the color also changes with the value of the volume fraction.

[0011] In the initial stage of the research, the inventor studied the gas-liquid two-phase distribution cloud map and the variation map of the number of interface grid nodes (i.e., the grid nodes corresponding to the gas-liquid interface) with the radial distance (the meaning is shown in Figure 7 ) for different internal flow fields of thin-film evaporators, as follows:

[0012] Example 1: The structure of the internal flow field of the thin-film evaporator is simple, the liquid film is a flat liquid film, and there are no liquid clusters; Figure 8 (a) is the gas-liquid two-phase distribution cloud map of the axial section of Figure 7 . The position near the wall on the left side is the liquid film, and the volume fraction is 1, showing red; the position far from the wall on the right side is the gas phase, and the volume fraction is 0, showing blue; there is no gas-liquid interface in the above two parts, so the number of interface grid nodes is 0; and the middle transitional color part is the gas-liquid interface part. In this part, the number of interface grid nodes is non-zero, and since the gas-liquid interface is vertically distributed, there are more interface grid nodes when counting along the radial direction; therefore, after counting the number of interface grid nodes at 3 different positions in the radial direction, the variation map of the number of interface grid nodes with the radial distance as shown in Figure 8 (b) will be obtained. There is a peak in this map, and the position corresponding to this peak is the gas-liquid interface part;

[0013] Example 2: The structure of the internal flow field of the thin-film evaporator is relatively complex, the liquid film includes a flat liquid film part and a liquid film protrusion part, and there are no liquid clusters; Figure 9 (a) is the gas-liquid two-phase distribution cloud map of the axial section of Figure 7 , Figure 9 (b) is the variation map of the number of interface grid nodes with the radial distance. There is a peak in this map, and the position corresponding to this peak is the gas-liquid interface position of the flat liquid film part;

[0014] Example 3: The structure of the internal flow field of the thin-film evaporator is complex, the liquid film includes a flat liquid film part and a liquid film protrusion part, and there are liquid clusters; Figure 10 (a) is the gas-liquid two-phase distribution cloud map of the axial section of Figure 7 , Figure 10(b) is the variation map of the number of interface grid nodes with the radial distance. There are two peaks in this map. One peak corresponds to the position near the liquid film surface, and the other peak corresponds to the interaction region between the liquid mass and the liquid film;

[0015] The internal flow field structure of the thin film evaporator for high-viscosity materials is complex. The liquid film includes a flat liquid film part and a protruding part of the liquid film, and there are liquid masses. Therefore, there will be two peaks in the variation map of the number of interface grid nodes with the radial distance. One peak corresponds to the position near the liquid film surface, and the other peak corresponds to the interaction region between the liquid mass and the liquid film. Using this feature, the interaction region between the liquid mass and the liquid film in the internal flow field of the thin film evaporator for high-viscosity materials can be determined.

[0016] However, Figure 8 、 9 10 can only represent a partial area of a single axial cross-section in the flow field. However, the spatial distribution of the internal flow field of the thin film evaporator for high-viscosity materials is very complex, and the flow fields in the circumferential and axial directions are different everywhere. The morphology and characteristics of the internal overall flow field cannot be characterized by the data of such a few simple cross-sections.

[0017] Therefore, the inventor divides the internal flow field (three-dimensional vertical cylindrical barrel) of the thin film evaporator for high-viscosity materials into n coaxial, mutually sleeved three-dimensional vertical sub-cylindrical barrels with a wall thickness of t, and then determines the number of interface grid nodes of each three-dimensional vertical sub-cylindrical barrel. However, a new problem arises. On the one hand, if the internal flow field of the thin film evaporator for high-viscosity materials is very large, the number of grid nodes will also be too large, resulting in a large number of interface grid nodes in each three-dimensional vertical sub-cylindrical barrel, making it difficult to draw the variation map of the number of interface grid nodes with the radial distance. On the other hand, the sizes of the grid nodes at different positions may not be the same during the meshing process; if the model is large, grid encryption will be performed at key parts, and the grid size at non-key parts can be moderate, which leads to differences in the grid density between different three-dimensional vertical sub-cylindrical barrels. Simply counting the number of interface grid nodes of each three-dimensional vertical sub-cylindrical barrel cannot accurately measure the interface situation in each cylindrical barrel region. Therefore, the inventor proposes to use "the percentage of the number of interface grid nodes of a three-dimensional vertical sub-cylindrical barrel in the total number of grid nodes of a certain three-dimensional vertical sub-cylindrical barrel" to replace "the number of interface grid nodes of a certain three-dimensional vertical sub-cylindrical barrel".

[0018] Now, the solution of the present invention will be specifically described:

[0019] Method for identifying interaction region in internal flow field of thin-film evaporator for high-viscosity (i.e., viscosity is 50 - 20000 Pa·s) materials. The shape of the internal flow field of the thin-film evaporator is a three-dimensional vertical cylindrical tube (the outer wall of the three-dimensional vertical cylindrical tube is equivalent to the inner wall of the thin-film evaporator, and the inner wall of the three-dimensional vertical cylindrical tube is equivalent to the cylindrical surface of the rotating shaft in the thin-film evaporator). The clearance width of the thin-film evaporator (i.e., the distance between the blade and the inner wall of the thin-film evaporator) is d, and the method includes the following steps;

[0020] (1) Perform meshing on the three-dimensional vertical cylindrical tube;

[0021] (2) Divide the three-dimensional vertical cylindrical tube into n coaxial, mutually sleeved three-dimensional vertical sub-cylindrical tubes with a wall thickness of t (i.e., the division width), where t ≤ d / 4. The division width should not be too large, otherwise the number of sampling points will be too small to accurately reflect the variation law at different radial positions. Therefore, in the present invention, the division width is controlled not to be greater than one-fourth of the clearance width;

[0022] (3) After obtaining the gas-liquid two-phase distribution cloud map of the i-th three-dimensional vertical sub-cylindrical tube, count the total number B of grid nodes corresponding to the gas-liquid interface i and the total number A of grid nodes of the i-th three-dimensional vertical sub-cylindrical tube i , and calculate the interface grid node ratio C of the i-th three-dimensional vertical sub-cylindrical tube i , C i = B i / A i × 100%, i = 1, 2,..., n, and the larger i is, the closer it is to the central axis of the three-dimensional vertical cylindrical tube;

[0023] (4) Plot a graph with the abscissa being i or a parameter related to i and the ordinate being C iFor the spectrum diagram, find the highest peak and the second-highest peak on the spectrum diagram. The peak that appears the latest among the highest peak and the second-highest peak is denoted as peak P. The three-dimensional vertical sub-cylindrical tube corresponding to the starting point of peak P, the three-dimensional vertical sub-cylindrical tube corresponding to the ending point of peak P, and the three-dimensional vertical sub-cylindrical tubes between these two three-dimensional vertical sub-cylindrical tubes together constitute the interaction region between the liquid mass and the liquid film. The reason for such division is as follows: ① The flow field analysis of the present invention requires knowing which side is the liquid film and which side is the liquid mass. The interaction region of the present invention is equivalent to the boundary between the liquid film and the liquid mass. Once this is found, it is known that one side is the liquid film and the other side is the liquid mass. ② The interaction region itself is responsible for the mass exchange between the liquid mass and the liquid film. Only with this region can the present invention count the situation of the mass exchange between the liquid mass and the liquid film, such as how the exchange occurs and whether the degree is intense, etc. ③ The traditional division method is to use a cross-section, an axial cross-section or a radial interface, and then use a method similar to image processing to divide. This is only applicable when the flow field is very regular. Now the involved flow field is very complex, and the distribution of the flow field is different everywhere in the three-dimensional space. It is impossible to use a single certain or several interfaces to represent the entire flow field. Therefore, the traditional methods are not applicable. The method of the present invention is based on data processing in the three-dimensional space. The only method for three-dimensional data processing and analyzing the interface is the method of the present invention, and there is no other.

[0024] As a preferred technical solution:

[0025] For the method for identifying the interaction region in the internal flow field of the thin-film evaporator for high-viscosity materials as described above, t ≤ d / 16. To improve the accuracy, it is preferably that the segmentation width should be one-sixteenth or less of the gap width. For example, Figure 11 in the thin-film evaporator, the gap width, i.e., d, is 4 mm, and the maximum segmentation width should not be greater than 0.25 mm.

[0026] For the method for identifying the interaction region in the internal flow field of the thin-film evaporator for high-viscosity materials as described above, t > s, where s is the maximum value of the lengths of the connecting lines between any two points in the smallest grid nodes. For example, if the grid size at the wall surface of the thin-film evaporator is in the range of 0.1 - 0.2 mm, the segmentation width should be greater than 0.2 mm. In this way, it can be ensured that the three-dimensional vertical sub-cylindrical tubes wrap the smallest grid nodes, avoiding data loss. There are many shapes of grid nodes. The common two-dimensional grid nodes are triangular and quadrilateral grids, and the common three-dimensional grid nodes are tetrahedron, hexahedron, prism, pyramid, and polyhedron grids.

[0027] For the method for identifying the interaction region in the internal flow field of the thin-film evaporator for high-viscosity materials as described above, the grid nodes correspond to the pixel points of the gas-liquid two-phase distribution cloud map.

[0028] The method for identifying the interaction region in the internal flow field of a thin-film evaporator for high-viscosity materials as described above. Each pixel point in the gas-liquid two-phase distribution cloud map has corresponding volume fraction data. The volume fraction is the ratio of the volume of the liquid phase at each grid node to the total volume of the liquid phase and the gas phase. The grid nodes corresponding to the gas-liquid interface are the pixel points with a volume fraction of 0.4 - 0.6 in the gas-liquid two-phase distribution cloud map.

[0029] The method for identifying the interaction region in the internal flow field of a thin-film evaporator for high-viscosity materials as described above. The grid nodes corresponding to the gas-liquid interface are the pixel points with a volume fraction of 0.45 - 0.55 in the gas-liquid two-phase distribution cloud map to obtain higher accuracy.

[0030] The method for identifying the interaction region in the internal flow field of a thin-film evaporator for high-viscosity materials as described above. The parameter related to i is the distance between the outer wall of the i-th three-dimensional vertical sub-cylindrical barrel and the outer wall of the first three-dimensional vertical sub-cylindrical barrel.

[0031] The method for identifying the interaction region in the internal flow field of a thin-film evaporator for high-viscosity materials as described above. The graph is a line graph or a bar graph, preferably a line graph because it is easier to determine the starting point and the ending point of peak P.

[0032] Beneficial effects

[0033] (1) The method for identifying the interaction region in the internal flow field of a thin-film evaporator for high-viscosity materials of the present invention can accurately obtain the interaction region between the internal liquid film and the liquid mass in the complex flow field formed by a real large-capacity thin-film evaporator, and then distinguish the liquid film distribution area and the liquid mass distribution area to complete the structural division of the flow field of the thin-film evaporator.

[0034] (2) The method for identifying the interaction region in the internal flow field of a thin-film evaporator for high-viscosity materials of the present invention can subsequently identify the shape of the liquid film and measure the thickness of the liquid film according to the area where the liquid film is distributed.

[0035] (3) The method for identifying the interaction region in the internal flow field of a thin-film evaporator for high-viscosity materials of the present invention can also subsequently count the volume of the liquid mass, estimate the mass transfer efficiency of the interaction region, and on this basis evaluate the evaporation capacity of the thin-film evaporator and realize the optimal design of the structure and process. Description of the drawings

[0036] Figure 1 It is the gas-liquid volume fraction cloud map (radial view) inside the scraping thin-film evaporator. Blue is the gas phase, red is the liquid phase, and the color is the gas-liquid interface.

[0037] Figure 2 It is the schematic diagram of the in-line scraper blade structure inside the scraping thin-film evaporator.

[0038] Figures 3 - 4 It is a schematic diagram of the theoretical distribution of the flow field pattern; Figure 3 In it, the arrow direction is the scraping plate movement direction and the rolling direction of the loop wave, Figure 4 In it, the arrow direction is the scraping plate movement direction;

[0039] Figure 5 It is a schematic diagram of the complex blade rotor structure used when the production capacity is relatively high;

[0040] Figure 6 is a schematic diagram of the internal flow field of the thin film evaporator in the present invention; among them, Figure (a) is a schematic diagram of the three-dimensional flow field structure, and Figure (b) is an axial local gas-liquid two-phase distribution cloud map;

[0041] Figure 7 It is a schematic diagram of the radial distance, and the arrow direction is along the radial distance direction;

[0042] Figure 8 It is a schematic diagram of Example 1; among them, Figure (a) is Figure 7 The gas-liquid two-phase distribution cloud map of the axial section of, and Figure (b) is the variation map of the number of interface grid nodes with the radial distance;

[0043] Figure 9 It is a schematic diagram of Example 2; among them, Figure (a) is Figure 7 The gas-liquid two-phase distribution cloud map of the axial section of, and Figure (b) is the variation map of the number of interface grid nodes with the radial distance;

[0044] Figure 10 It is a schematic diagram of Example 3; among them, Figure (a) is Figure 7 The gas-liquid two-phase distribution cloud map of the axial section of, and Figure (b) is the variation map of the number of interface grid nodes with the radial distance;

[0045] Figures 11 - 12 It is the variation map of the number of interface grid nodes with the radial distance under different gaps;

[0046] Among them, 1-liquid mass, 2-liquid film, 3-loop wave, 4-blade, 5-cylindrical surface of the rotating shaft, 6-inner wall of the thin film evaporator. Specific embodiments

[0047] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it 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 also fall within the scope defined by the appended claims of this application.

[0048] A method for identifying the interaction region in the internal flow field of a thin film evaporator for high-viscosity materials, the specific steps are as follows:

[0049] (1) Meshing:

[0050] As Figure 1 shown, the shape of the internal flow field of the thin-film evaporator is a three-dimensional vertical cylinder (the outer wall of the three-dimensional vertical cylinder is equivalent to the inner wall 6 of the thin-film evaporator, and the inner wall of the three-dimensional vertical cylinder is equivalent to the cylindrical surface 5 of the rotating shaft in the thin-film evaporator); mesh the three-dimensional vertical cylinder, that is, generate a full-field mesh, and locally refine the mesh at key positions such as the wall surface, the gap between the blade 4 and the inner wall 6 of the thin-film evaporator, and then automatically fill it with volume meshes. The filling mesh form can adopt various structural forms such as tetrahedron, hexahedron, and the combination of hexahedron and polyhedron;

[0051] (2) Divide the cylinder:

[0052] Divide the three-dimensional vertical cylinder into n coaxial, nested, and equally thick three-dimensional vertical sub-cylinders with a wall thickness of t, where s < t ≤ d / 16; where d is the gap width of the thin-film evaporator (i.e., the distance between the blade and the inner wall of the thin-film evaporator), and s is the maximum value of the length of the line connecting any two points among the smallest grid nodes;

[0053] (3) Calculate the proportion of interface grid nodes:

[0054] Obtain the gas-liquid two-phase distribution cloud map of the i-th three-dimensional vertical sub-cylinder. The pixel points of the gas-liquid two-phase distribution cloud map are grid nodes; count the total number B of grid nodes corresponding to the gas-liquid interface i and the total number A of grid nodes of the i-th three-dimensional vertical sub-cylinder i , and calculate the proportion C of the interface grid nodes of the i-th three-dimensional vertical sub-cylinder through calculation i , C i = B i / A i × 100%, i = 1, 2,..., n, the larger i is, the closer it is to the central axis of the three-dimensional vertical cylinder; among them, each pixel point of the gas-liquid two-phase distribution cloud map has corresponding volume fraction data, and the volume fraction is the ratio of the volume of the liquid phase at each grid node to the total volume of the liquid phase and the gas phase; the grid nodes corresponding to the gas-liquid interface are the pixel points with a volume fraction of 0.45 - 0.55 in the gas-liquid two-phase distribution cloud map;

[0055] (4) Draw the graph and judge the interaction area:

[0056] Draw a graph with the abscissa being i or a parameter related to i and the ordinate being C iFor the atlas, find the highest peak and the second highest peak on the atlas. The peak that appears latest among the highest peak and the second highest peak is denoted as peak P. The three-dimensional vertical sub-cylindrical tube corresponding to the starting point of peak P, the three-dimensional vertical sub-cylindrical tube corresponding to the ending point of peak P, and the three-dimensional vertical sub-cylindrical tubes between these two three-dimensional vertical sub-cylindrical tubes together constitute the interaction region between the liquid mass and the liquid film; wherein, the parameter related to i is the distance between the outer wall of the i-th three-dimensional vertical sub-cylindrical tube and the outer wall of the first three-dimensional vertical sub-cylindrical tube.

[0057] Using the method of the present invention, the present invention respectively obtained the variation atlas of the proportion of interface grid nodes in the internal flow field of the thin-film evaporator with d = 4 mm with respect to the radial distance (as Figure 11 shown) and the variation atlas of the proportion of interface grid nodes in the internal flow field of the thin-film evaporator with d = 5.5 mm with respect to the radial distance (as Figure 12 shown). There are two peaks in the figures, and the position corresponding to the second peak is the interaction region between the liquid mass and the liquid film.

[0058] After identifying the interaction region between the liquid mass and the film, the flow field region can be morphologically divided. The two sides of the interaction region are the liquid film region and the liquid mass region respectively. As Figures 11 - 12 shown, if the radial distance of 0 represents the wall position, then the left side of the interaction region is the liquid film region, and the right side of the interaction region is the liquid mass region.

Claims

1. A method for identifying the interaction region in the internal flow field of a thin film evaporator for high-viscosity materials, wherein the shape of the internal flow field of the thin film evaporator is a three-dimensional vertical cylinder, and the gap width of the thin film evaporator is d, characterized in that: The steps include: (1) Meshing the three-dimensional vertical cylinder; (2) dividing the three-dimensional vertical cylindrical tube into n coaxial, mutually nested three-dimensional vertical sub-cylindrical tubes with a wall thickness of t, t≤d / 4; (3) After obtaining the gas-liquid two-phase distribution cloud map of the i-th three-dimensional vertical sub-cylinder, count the total number of grid nodes corresponding to the gas-liquid interface B i and the total number of mesh nodes A of the i-th three-dimensional vertical sub-cylinder i , the interface mesh node ratio C of the i-th three-dimensional vertical sub-cylinder is calculated i , C i =B i / A i ×100%, i=1,2,...,n, the larger i is, the closer it is to the central axis of the three-dimensional vertical cylinder; (4) Plot the horizontal axis as i or the parameter related to i and the vertical axis as C i , find the highest peak and the second highest peak from the spectrum, and the latest peak among the highest peak and the second highest peak is recorded as peak P. The three-dimensional vertical sub-cylinder corresponding to the starting point of peak P, the three-dimensional vertical sub-cylinder corresponding to the end point of peak P, and the three-dimensional vertical sub-cylinder between these two three-dimensional vertical sub-cylinders together constitute the interaction area between the liquid mass and the liquid film.

2. The method for identifying the interaction area in the internal flow field of a thin film evaporator for high-viscosity materials according to claim 1, characterized in that: t≤d / 16.

3. The method for identifying the interactive area in the internal flow field of a thin film evaporator for high-viscosity materials according to claim 1, characterized in that: t>s, s is the maximum length of the line connecting any two points in the minimum grid node.

4. The method for identifying the interaction area in the internal flow field of a thin film evaporator for high-viscosity materials according to claim 1, characterized in that: The grid nodes correspond to the pixels of the gas-liquid two-phase distribution cloud map.

5. The method for identifying the interactive area in the internal flow field of a thin film evaporator for high-viscosity materials according to claim 4, characterized in that: Each pixel point of the gas-liquid two-phase distribution cloud map has corresponding volume fraction data, and the volume fraction is the ratio of the volume of the liquid phase at each grid node to the total volume of the liquid phase and the gas phase; the grid node corresponding to the gas-liquid interface is the pixel point with a corresponding volume fraction of 0.4 to 0.6 in the gas-liquid two-phase distribution cloud map.

6. The method for identifying the interactive area in the internal flow field of a thin film evaporator for high-viscosity materials according to claim 5, characterized in that: The grid nodes corresponding to the gas-liquid interface are the pixels with volume fractions of 0.45 to 0.55 in the gas-liquid two-phase distribution cloud map.

7. The method for identifying the interactive area in the internal flow field of a thin film evaporator for high-viscosity materials according to claim 1, characterized in that: The parameter associated with i is the distance between the outer wall of the i-th three-dimensional vertical sub-cylindrical tube and the outer wall of the first three-dimensional vertical sub-cylindrical tube.

8. The method for identifying the interactive area in the internal flow field of a thin film evaporator for high-viscosity materials according to claim 1, characterized in that: The graph is a line graph or a bar graph.

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