Dynamic simulation method for heat flow field in door opening and closing process of straight-through type oven

Abstract

The invention relates to a heat flow field dynamic simulation method in the door opening and closing process of a straight-through type oven. Comprising the steps that a three-dimensional model of the straight-through type oven is built, and the three-dimensional model is simplified; an external environment computational domain is constructed outside the oven according to the actual size of a workshop, ANSYS Fluent software is used for constructing an overall simulation model of the straight-through oven and the external environment computational domain, and a Fluent pretreatment module is used for carrying out grid division on the simulation model; setting an initial boundary condition according to the process parameters, activating Dynamic Mesh Events, and setting Event according to a simulation process; performing heat flow field simulation in the door opening and closing process of the straight-through type drying oven to obtain temperature field distribution in the door opening and closing process of the straight-through type drying oven, and further obtaining a temperature curve of a temperature measurement point in the door opening and closing process of the straight-through type drying oven; a simulation result is analyzed, and structural design optimization is guided; simulation results are analyzed, structural design optimization is guided, and the simulation efficiency is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal flow field simulation, in particular to a thermal flow field dynamic simulation method for a straight-through oven door opening and closing process. Background Art

[0002] Floor-standing ovens are generally composed of a chamber, hot air circulation system, heating device, temperature control system, inlet and outlet sealed doors, etc. Since the temperature of the effective space inside the oven is higher than the temperature of the outside and surrounding equipment, the hot air inside the oven and the cold air outside produce strong convection during the opening and closing of the inlet and outlet doors, which affects the distribution of the heat flow field inside the oven; at the same time, a large amount of hot air will also be emitted from the inlet and outlet, increasing the energy consumption of the oven equipment. Therefore, it is necessary to conduct dynamic simulation of the heat flow field of the oven during the opening and closing process to understand the distribution of the heat flow field during the opening and closing process and guide the structural optimization of the oven.

[0003] At present, most of the numerical simulation studies on ovens are studies on the internal thermal flow field of the oven in steady state, and there is a lack of research on the interaction between the internal thermal flow field and the external environment during the opening and closing of the oven door. In addition, in fluid simulation research, the opening and closing process of the door usually requires the internal grid to be renormalized after the boundary conditions are deformed during the calculation process, so that the quality of the deformed grid meets the calculation requirements. For large straight-through ovens, this technology has the disadvantages of large grid data and long calculation time, and the overall simulation efficiency is low.

[0004] Therefore, it is urgent to find a new method to study the thermal flow field distribution of the straight-through oven during the opening and closing process and to improve the simulation efficiency. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for dynamic simulation of the thermal flow field in the process of opening and closing the door of a straight-through oven, so as to realize the dynamic simulation of the straight-through oven in the process of opening and closing the door and improve the simulation efficiency, so as to better study the distribution of the thermal flow field in the process of opening and closing the door of the straight-through oven.

[0006] The present invention solves the technical problem by adopting the following technical solutions:

[0007] A method for dynamic simulation of thermal flow field during the door opening and closing process of a straight-through oven comprises the following steps:

[0008] S1. Build a three-dimensional model of a straight-through oven, which includes the oven chamber, hot air circulation system, inlet and outlet contour doors, internal partition doors, and the external calculation domain of the oven, and simplify the three-dimensional model;

[0009] S2. Construct an external environment calculation domain outside the oven according to the actual size of the workshop building, use ANSYS Fluent software to build an overall simulation model of the straight-through oven and the external environment calculation domain, and use the Fluent pre-processing module to perform mesh division of the simulation model;

[0010] S3, set initial boundary conditions according to process parameters, activate Dynamic Mesh Events, and set Event according to the simulation process;

[0011] S4, performing a thermal flow field simulation of the straight-through oven during the process of opening and closing the door, obtaining the distribution of the temperature field of the straight-through oven during the process of opening and closing the door, and then obtaining the temperature curve of the temperature measuring point of the straight-through oven during the process of opening and closing the door;

[0012] S5. Analyze simulation results and guide structural design optimization.

[0013] Furthermore, the simplification of the three-dimensional model in step S1 includes:

[0014] (1) The air inside and outside the oven is considered as incompressible gas;

[0015] (2) Automatic sealing doors are set at the inlet and outlet of the straight-through oven. After the inlet and outlet doors of the oven are closed, the influence of wind penetration through the doors is not considered; at the same time, the inlet and outlet sealing doors are not established in the geometric model;

[0016] (3) Establish the external environment calculation domain outside the oven according to the actual size of the workshop building, assume that the air flow field in the workshop building is stable, and simplify other equipment in the workshop;

[0017] (4) The influence of the exhaust system is not considered in the modeling process;

[0018] (5) In the process of establishing the three-dimensional model of the oven, small geometric features that have no effect on the flow field simulation are ignored, including but not limited to screws and corners.

[0019] Moreover, in the step S2, the three-dimensional model is imported into the Fluent pre-processing module to build an overall simulation model of the straight-through oven and the external environment calculation domain, and meshing is performed. The overall tetrahedral mesh is mainly used. Considering the size of the oven equipment and the range of the external calculation domain, the average grid scale of the internal calculation domain and the air duct of the oven is set to 100 mm, and the average grid scale of the external calculation domain of the oven is set to 200 mm, with a total number of 2.33 million grids.

[0020] Moreover, in step S3, the calculation model initial boundary condition setting includes:

[0021] (1) Transient calculation of Realizable k-e turbulence model;

[0022] (2) The default wall surface in the calculation domain is Wall. The thermal insulation material of the oven chamber is rock wool, with a specific heat capacity of 750 J / (kg·K), a thermal conductivity of 0.04 W / (m·K), and a density of 100 kg / m 3 , so the external surface coefficient is set to 1.276W / (m 2 ·℃), and the rest of the walls are set as adiabatic walls;

[0023] (3) The air inlet was set to velocity inlet v = 13 m / s, and the air temperature was set to 180 °C;

[0024] (4) The return air outlet is set as the free outflow boundary.

[0025] Moreover, the entire simulation process is divided into 5 stages, including:

[0026] (1) The temperature inside the chamber rises to 180°C and is kept warm for a period of time, which takes a total of 300 seconds;

[0027] (2) The entrance door is simulated to open and the workpiece enters the process, which takes a total of 150 seconds;

[0028] (3) After 2.5 minutes, the inlet door is closed, the temperature inside the chamber is raised to 180°C and kept warm for a period of time, which takes a total of 180 seconds;

[0029] (4) The exit door is simulated to open and the workpiece leaves the room, which takes 150 seconds in total;

[0030] (5) After 2.5 minutes, the exit door is closed and the temperature inside the chamber is raised to 180°C and kept warm for a period of time, which takes a total of 210 seconds.

[0031] Moreover, in the Fluent software Dynamic Mesh, activate the Event definition panel. The steps to define the Event according to the simulation process are:

[0032] (1) At 300 seconds, use TUI Command to change the inlet gate boundary condition from Wall to free outflow boundary;

[0033] (2) At 450s, the boundary condition of the inlet gate is changed to Wall;

[0034] (3) At 630 seconds, use TUI Command to change the exit gate boundary condition from Wall to Free Outflow boundary;

[0035] (4) At 780s, change the exit gate boundary condition to Wall.

[0036] The advantages and positive effects of the present invention are:

[0037] 1. The present invention can guide the dynamic simulation research of the heat flow field of the straight-through oven during the process of opening and closing the door, so as to grasp the distribution of the heat flow field during the process of opening and closing the door and guide the structural optimization of the oven.

[0038] 2. The present invention realizes the conversion of boundary types of the inlet and outlet doors of the straight-through oven during the opening and closing process based on the EVENT function provided by the dynamic grid module of the Fluent software to simulate the opening and closing process of the door, thereby realizing the dynamic simulation of the straight-through oven during the opening and closing process, avoiding the internal grid renormalization after the boundary conditions change in the traditional method, greatly improving the simulation efficiency, and being able to better study the heat flow field distribution of the straight-through oven during the opening and closing process.

[0039] 3. The present invention sets initial boundary conditions for process parameters, optimizes the boundary conditions to activate Dynamic Mesh Events, and sets Events according to the simulation process to achieve dynamic simulation of the straight-through oven during the opening and closing process, thereby further improving the simulation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a parameter diagram of the straight-through oven model of the present invention.

[0041] Figure 2 This is a dynamic simulation flow chart of the door opening and closing process of the straight-through oven of the present invention.

[0042] Figure 3 It is a three-dimensional model diagram of the straight-through oven of the present invention and the external environment calculation domain.

[0043] Figure 4 This is a grid division diagram of the straight-through oven of the present invention.

[0044] Figure 5 This is a grid division diagram of the external calculation domain of the straight-through oven of the present invention.

[0045] Figure 6 This is a temperature field distribution diagram when the inlet door is opened during the simulation process of the straight-through oven of the present invention.

[0046] Figure 7 This is a temperature field distribution diagram when the outlet door is opened during the simulation process of the straight-through oven of the present invention.

[0047] Figure 8 It is a temperature curve diagram of the temperature measuring points during the simulation process of the straight-through oven of the present invention. DETAILED DESCRIPTION

[0048] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0049] A method for dynamic simulation of thermal flow field during the door opening and closing process of a straight-through oven comprises the following steps:

[0050] S1. Build a three-dimensional model of a straight-through oven, which includes the oven chamber, hot air circulation system, inlet and outlet contour doors, internal partition doors, and the external calculation domain of the oven, and simplify the three-dimensional model;

[0051] S2. Construct an external environment calculation domain outside the oven according to the actual size of the workshop building, use ANSYS Fluent software to build an overall simulation model of the straight-through oven and the external environment calculation domain, and use the Fluent pre-processing module to perform mesh division of the simulation model;

[0052] S3, set initial boundary conditions according to process parameters, activate Dynamic Mesh Events, and set Event according to the simulation process;

[0053] S4, performing a thermal flow field simulation of the straight-through oven during the process of opening and closing the door, obtaining the distribution of the temperature field of the straight-through oven during the process of opening and closing the door, and then obtaining the temperature curve of the temperature measuring point of the straight-through oven during the process of opening and closing the door;

[0054] S5. Analyze simulation results and guide structural design optimization.

[0055] Example 1

[0056] 1. Build a three-dimensional model of the straight-through oven and the external environment calculation domain.

[0057] In the embodiment of the present invention, SolidWorks software is used to perform three-dimensional modeling of the experimental line oven. The model includes an oven chamber, a hot air circulation system, an inlet and outlet contour door, an internal partition door, and an oven external calculation domain. The model parameters are as follows: Figure 1 As shown, the model is Figure 3 As shown, and simplified according to actual conditions.

[0058] The main simplifications are: (1) The air inside and outside the oven is considered to be incompressible gas.

[0059] (2) In the embodiment of the present invention, automatic sealing doors are set at the inlet and outlet positions of the straight-through oven, and the doors have good airtightness, so the influence of wind penetration through the doors is not considered after the inlet and outlet doors of the oven are closed; at the same time, in order to reduce the amount of calculation, the EVENT function provided by the FLUENT dynamic mesh module is used in the calculation process to realize the conversion of the boundary type of the inlet and outlet door positions to simulate the opening and closing process of the door. Therefore, the inlet and outlet sealing doors are not established in the geometric model.

[0060] (3) Considering the heat exchange between the internal heat flow field and the external environment after the oven door is opened, an external calculation domain is established outside the oven according to the actual size of the workshop building. It is assumed that the air flow field in the workshop building is stable, and other equipment in the workshop is simplified.

[0061] (4) Assumptions of the exhaust system: In the embodiment of the present invention, the exhaust air volume of the oven accounts for 3% of the oven volume. For a large floor-standing oven, the proportion is even smaller. Therefore, the influence of the exhaust system is not considered in the modeling process in this example.

[0062] (5) Simplification of structural details: In the process of establishing the three-dimensional model of the oven, small geometric features that have no effect on the flow field simulation, such as screws, corners, etc., are ignored.

[0063] 2. Import the 3D model into the Fluent pre-processing module to build an overall simulation model of the straight-through oven and the external environment calculation domain, and perform mesh division. The overall mesh is mainly tetrahedral. Considering the size of the oven equipment and the range of the external calculation domain, the average mesh scale of the oven internal calculation domain and the air duct is set to 100mm, and the average mesh scale of the oven external calculation domain is set to 200mm. The total number of meshes is 2.33 million, as shown in the following figure. Figure 4 , Figure 5 shown.

[0064] 3. Set the initial boundary conditions of the simulation model:

[0065] For conventional fluid calculations, the initial boundary condition settings of the calculation model include: (1) transient calculation of Realizable ke turbulence model;

[0066] (2) The default wall surface in the calculation domain is Wall. The thermal insulation material of the oven chamber is rock wool, with a specific heat capacity of 750 J / (kg·K), a thermal conductivity of 0.04 W / (m·K), and a density of 100 kg / m 3 , so the external surface coefficient is set to 1.276W / (m 2 ·℃), and the rest of the walls are set as adiabatic walls;

[0067] (3) The air inlet was set to velocity inlet v = 13 m / s, and the air temperature was set to 180 °C;

[0068] (4) The return air outlet is set as the free outflow boundary.

[0069] 4. Clarify the simulation process:

[0070] According to the operation process of the oven equipment in the example, the entire simulation process is divided into 5 stages. Figure 2 As shown:

[0071] (1) The temperature inside the chamber rises to 180°C and is kept warm for a period of time, which takes a total of 300 seconds;

[0072] (2) The entrance door is simulated to open and the workpiece enters the process, which takes a total of 150 seconds;

[0073] (3) After 2.5 minutes, the inlet door is closed, the temperature inside the chamber is raised to 180°C and kept warm for a period of time, which takes a total of 180 seconds;

[0074] (4) The exit door is simulated to open and the workpiece leaves the room, which takes 150 seconds in total;

[0075] (5) After 2.5 minutes, the exit door is closed and the temperature inside the chamber is raised to 180°C and kept warm for a period of time, which takes a total of 210 seconds.

[0076] 5. Define Event

[0077] Activate the Event definition panel in the Fluent software Dynamic Mesh and define the Event according to the simulation process:

[0078] (1) At 300 seconds, use TUI Command to change the inlet gate boundary condition from Wall to free outflow boundary;

[0079] (2) At 450s, the boundary condition of the inlet gate is changed to Wall;

[0080] (3) At 630 seconds, use TUI Command to change the exit gate boundary condition from Wall to Free Outflow boundary;

[0081] (4) At 780s, change the exit gate boundary condition to Wall.

[0082] 6. Conduct dynamic simulation of thermal flow field during the opening and closing process of the straight-through oven.

[0083] 7. Post-process the simulation model to obtain the temperature curve of the oven control temperature measurement point, such as Figure 8 As shown in the figure, the simulation model is cross-validated with the actual temperature curve to verify the rationality of the simulation model; then the temperature distribution cloud diagram of the opening and closing process of the inlet and outlet doors of the straight-through oven is output, as shown in the figure. Figure 6 , Figure 7 As shown in the figure, the mutual influence between the temperature field distribution inside the oven and the external environment during the opening and closing process of the oven door is analyzed to guide the optimization of the structural design.

[0084] This method is based on the EVENT function provided by the dynamic mesh module of the Fluent software to realize the conversion of boundary types of the inlet and outlet doors of the straight-through oven during the opening and closing process to simulate the opening and closing process of the door, thereby realizing the dynamic simulation of the straight-through oven during the opening and closing process and improving the simulation efficiency, so as to better study the heat flow field distribution of the straight-through oven during the opening and closing process.

[0085] Although the embodiments of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments.

Claims

1. A method for dynamic simulation of thermal flow field during the opening and closing process of a straight-through oven, characterized in that: The steps include: S1. Build a three-dimensional model of a straight-through oven, which includes the oven chamber, hot air circulation system, inlet and outlet contour doors, internal partition doors, and the external calculation domain of the oven, and simplify the three-dimensional model; S2. Construct an external environment calculation domain outside the oven according to the actual size of the workshop building, use ANSYS Fluent software to build an overall simulation model of the straight-through oven and the external environment calculation domain, and use the Fluent pre-processing module to perform mesh division of the simulation model; S3, set initial boundary conditions according to process parameters, activate Dynamic Mesh Events, and set Event according to the simulation process; S4, performing a thermal flow field simulation of the straight-through oven during the process of opening and closing the door, obtaining the distribution of the temperature field of the straight-through oven during the process of opening and closing the door, and then obtaining the temperature curve of the temperature measuring point of the straight-through oven during the process of opening and closing the door; S5. Analyze simulation results and guide structural design optimization.

2. The method for dynamic simulation of thermal flow field during the door opening and closing process of a straight-through oven according to claim 1, characterized in that: The simplification of the three-dimensional model in step S1 includes: (1) The air inside and outside the oven is considered as incompressible gas; (2) Automatic sealing doors are set at the inlet and outlet of the straight-through oven. After the inlet and outlet doors of the oven are closed, the influence of wind penetration through the doors is not considered; at the same time, the inlet and outlet sealing doors are not established in the geometric model; (3) Establish the external environment calculation domain outside the oven according to the actual size of the workshop building, assume that the air flow field in the workshop building is stable, and simplify other equipment in the workshop; (4) The influence of the exhaust system is not considered in the modeling process; (5) In the process of establishing the three-dimensional model of the oven, small geometric features that have no effect on the flow field simulation are ignored, including but not limited to screws and corners.

3. The method for dynamic simulation of thermal flow field during the door opening and closing process of a straight-through oven according to claim 2, characterized in that: In the step S2, the three-dimensional model is imported into the Fluent pre-processing module to build an overall simulation model of the straight-through oven and the external environment calculation domain, and meshing is performed. The overall tetrahedral mesh is mainly used. Considering the size of the oven equipment and the range of the external calculation domain, the average grid scale of the internal calculation domain and the air duct of the oven is set to 100 mm, and the average grid scale of the external calculation domain of the oven is set to 200 mm, with a total number of 2.33 million grids.

4. The method for dynamic simulation of thermal flow field during the door opening and closing process of a straight-through oven according to claim 3, characterized in that: In step S3, the initial boundary condition setting of the calculation model includes: (1) Transient calculation of Realizable k-e turbulence model; (2) The default wall surface in the calculation domain is Wall. The thermal insulation material of the oven chamber is rock wool, with a specific heat capacity of 750 J / (kg·K), a thermal conductivity of 0.04 W / (m·K), and a density of 100 kg / m 3 , so the external surface coefficient is set to 1.276W / (m 2 ·℃), and the rest of the walls are set as adiabatic walls; (3) The air inlet was set to velocity inlet v = 13 m / s, and the air temperature was set to 180 °C; (4) The return air outlet is set as the free outflow boundary.

5. The method for dynamic simulation of thermal flow field during the door opening and closing process of a straight-through oven according to claim 4, characterized in that: The entire simulation process is divided into five stages, including: (1) The temperature inside the chamber rises to 180°C and is kept warm for a period of time, which takes a total of 300 seconds; (2) The entrance door is simulated to open and the workpiece enters the process, which takes a total of 150 seconds; (3) After 2.5 minutes, the inlet door is closed, the temperature inside the chamber is raised to 180°C and kept warm for a period of time, which takes a total of 180 seconds; (4) The exit door is simulated to open and the workpiece leaves the room, which takes 150 seconds in total; (5) After 2.5 minutes, the exit door is closed and the temperature inside the chamber is raised to 180°C and kept warm for a period of time, which takes a total of 210 seconds.

6. The method for dynamic simulation of thermal flow field during the door opening and closing process of a straight-through oven according to claim 5, characterized in that: Activate the Event definition panel in the Fluent software Dynamic Mesh. The steps to define the Event according to the simulation process are as follows: (1) At 300 seconds, use TUICommand to change the inlet gate boundary condition from Wall to free outflow boundary; (2) At 450s, the boundary condition of the inlet gate is changed to Wall; (3) At 630 seconds, use TUI Command to change the exit gate boundary condition from Wall to free outflow boundary; (4) At 780s, change the exit gate boundary condition to Wall.

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