Method for predicting surface heat and humidity distribution condition of heat-setting process fabric

Abstract

The invention relates to a method for predicting the surface heat and humidity distribution condition of a heat-setting process fabric. The method comprises the following steps: constructing a drying box full-size model and a fabric pore structure model according to working conditions; fluid turbulence, heat and mass transfer and dynamic grid transient models are constructed to perform multi-physical field coupling of heat and humidity transfer between the fabric and the drying box; setting translation deformation and heat and mass transfer boundary conditions of the fabric and external boundary conditions of the drying box; defining material attributes of the fabric and air in the drying box; setting a calculation area based on a physical field related to the fabric pore structure model, and delimiting a movable grid area in the calculation area, so that the fabric moves in the drying box full-size model at a set speed according to a specified direction; grid division is carried out on the calculation area, simulation time and step length are set, and then the temperature and humidity distribution conditions when the airflow acts on the surface of the fabric are obtained through simulation. The method can effectively predict the heat and humidity distribution condition of the fabric surface, and provides a theoretical basis for heat setting process quality improvement.

Description

Technical Field

[0001] The invention relates to the technical field of thermal energy and power engineering, and in particular to a method for predicting heat and moisture distribution on the surface of a heat setting process fabric. Background Art

[0002] In the textile industry, drying of different types of fabrics is an important process in the pre-weaving sizing and post-printing and dyeing finishing operations. There are many types of drying equipment, such as drum dryers, hot air stenter frames, etc., all of which have the function of drying fabrics. When it comes to dehydration scenarios such as fabric drying and shaping, the existing drying device only analyzes the flow field of the air supply process, which is not completely in line with the actual engineering practice. At the same time, during the heat setting process, belt conveying is often used to ensure the continuity of the actual process. The heat and mass transfer process of the fabric is completed in a moving state. At the same time, during the heat setting process, the speed ratio of the transmission equipment is different with the different fiber varieties and finished product requirements. The movement of the fabric will cause uneven surface moisture distribution and local "mildew" and "dry spots", which seriously affects the quality of the finished fabric. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for predicting the heat and moisture distribution on the surface of a heat-setting process fabric, which can effectively predict the heat and moisture distribution on the surface of the fabric, and further provide a theoretical basis for parameter optimization of heat-setting equipment and improvement of process quality.

[0004] The technical solution adopted by the present invention to solve the technical problem is: to provide a method for predicting the heat and moisture distribution on the surface of a heat-setting process fabric, comprising the following steps: According to the working conditions of the heat setting process, a full-scale model of the drying oven and a model of the fabric pore structure were constructed; Construct fluid turbulence, heat and mass transfer, and dynamic mesh transient models, and conduct multi-physics coupling of heat and moisture transfer between the fabric pore structure model and the full-scale drying oven model; Set the translational deformation and heat and mass transfer boundary conditions of the fabric pore structure model, as well as the external boundary conditions of the full-scale drying oven model; Define the material properties of the fabric pore structure model and the material properties of the air in the full-scale model of the drying oven; The calculation area is set based on the physical field involved in the fabric pore structure model, and the dynamic grid area is delineated in the calculation area, so that the fabric pore structure model moves in the full-size model of the drying box in a specified direction and at a set speed; The calculation area is meshed and the simulation time and step size are set to simulate and obtain the temperature and humidity distribution when the airflow acts on the surface of the fabric pore structure model.

[0005] Furthermore, the calculation area is set as the vertical area between the fabric pore structure model and its upper and lower surfaces and the plane where the air outlet is located.

[0006] Furthermore, before the step of meshing the calculation area and setting the simulation time and step size, the step of defining a free jet area and a porous medium area in the calculation area is also included.

[0007] Furthermore, free tetrahedral meshes are used when meshing the fabric pore structure model.

[0008] Furthermore, before the step of simulating and analyzing the temperature and humidity distribution of the airflow acting on the surface of the fabric pore structure model, the step of extending the dynamic grid area by using a periodic extended boundary is also included.

[0009] Furthermore, after the step of simulating and analyzing the temperature and humidity distribution of the airflow acting on the surface of the fabric pore structure model, the method further includes the step of constructing a device for measuring the heat and humidity distribution on the fabric surface to verify the simulation results.

[0010] Furthermore, the device for measuring heat and moisture distribution on the surface of the fabric comprises a drying box, at least two air inlets are formed on the side wall of the drying box, each air inlet is detachably connected to an air duct, a tray bracket is arranged between two adjacent air ducts, and a plurality of air outlets are formed on a side of each air duct facing the tray bracket, and a hot air flow is sent into the air duct from the air inlet by an air supply device and then sprayed onto the fabric placed on the tray bracket through the air outlet for heat setting, a slide rail is arranged on the tray bracket to drive the fabric placed thereon to move along the slide rail during the heat setting process; the tray bracket is connected to a pressure transmitter to detect the mass change of the fabric placed thereon in real time; a sensor module is arranged in the air inlet to measure the temperature, humidity and wind speed of the hot air flow.

[0011] Furthermore, the plane where each air outlet is located is parallel to the fabric, and the formed air outlet area can completely cover the side of the fabric facing the air duct.

[0012] Furthermore, it also includes a temperature and humidity sensor array for detecting the heat and humidity distribution on the fabric surface.

[0013] Furthermore, an exhaust port is formed on the upper wall of the drying box near the air inlet for exhausting the hot air flow in the drying box.

[0014] Furthermore, a return air port is formed on the upper wall of the drying box away from the air inlet, and the return air port is connected to the air supply device through a return air duct. A desiccant is arranged in the return air duct. The hot air in the drying box flows into the return air duct through the return air port and flows back to the air supply device after being dehumidified by the dryer.

[0015] Beneficial Effects Due to the adoption of the above technical scheme, the present invention has the following advantages and positive effects compared with the prior art: the present invention constructs a transient model of fluid flow, heat and mass transfer process, and realizes the heat and moisture transfer process of the fabric in conjunction with the dynamic grid method, thereby supplementing the deficiencies in the existing model in the analysis of heat and mass transfer of objects in motion. The proposed numerical calculation method has strong versatility and operability, small calculation error, and convenient parameter adjustment, and can be widely applied to the actual process of various belt conveyor heat setting processes; the present invention constructs a thermophysical process model that combines multiple mutually coupled processes such as fluid flow, heat transfer and mass transfer, and sets simulation parameters according to the working conditions of the heat setting process. , which can accurately predict the uniformity of heat and moisture distribution on the surface of moving fabrics, thereby guiding the improvement of local mildew and dry spot problems of fabrics in the heat setting process; in addition, by dividing the dynamic grid area and other calculation areas during simulation, and using periodic extended boundaries to extend the grid area, it can effectively characterize the relative displacement of the fabric while saving calculation time. The method of regular graphic wrapping is used during simulation to solve the problem of vertex overlapping deformation caused by grid movement during calculation; the heat and moisture transfer of the fabric is coupled with the movement process to effectively characterize the heat and moisture distribution characteristics on the surface of the moving fabric, guiding the speed design of the continuous dryer and setting machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a flow chart of an embodiment of the present invention; Figure 2 It is a schematic diagram of the modeling and simulation process of an embodiment of the present invention; Figure 3 is a numerical calculation modeling diagram of an embodiment of the present invention; Figure 4 is a temperature and humidity uniformity distribution diagram of a fabric surface according to an embodiment of the present invention; Figure 5 It is a schematic diagram of the structure of an experimental verification device according to an embodiment of the present invention; Figure 6 Schematic diagram of fabric drying and surface heat and moisture distribution detection according to an embodiment of the present invention; Figure 7 Schematic diagram of replaceable air duct type according to an embodiment of the present invention. DETAILED DESCRIPTION

[0017] 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 are not intended 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 fall within the scope limited by the appended claims of the application equally.

[0018] The embodiment of the present invention relates to a method for predicting the heat and moisture distribution on the surface of a heat setting process fabric. Figure 1 As shown, the following steps are included: S1: Based on COMSOL software, fluid turbulence, heat and mass transfer, and dynamic mesh transient models were constructed to conduct multi-physics coupling of heat and moisture transfer in moving fabrics; S2: Determine the simulation parameters in the numerical calculation process according to the actual working conditions in the heat setting process; S3: Construct a full-scale model of the drying oven and a fabric pore structure model, and determine the translation deformation of the geometric model, the external boundary conditions of the drying oven, and the heat and mass transfer boundary conditions of the fabric; S4: Define the material properties of the porous fabric and the air in the drying box, delineate the dynamic mesh area, define the initial velocity for the fabric and move it in the drying box in the specified direction; S5: Based on the physical fields involved in the geometric model, use free tetrahedral mesh to mesh the geometric model and set the total solution time and step size; S6: Post-process the simulation results to analyze the temperature and humidity distribution of the fabric surface under the action of high-speed airflow.

[0019] Among them, the fluid turbulence model is used to simulate the flow state of air in the drying box, and the turbulence effect is considered to accurately describe the complex behavior of the airflow. The heat and mass transfer model is used to analyze the heat and moisture exchange process between the fabric and the air, including convection, radiation, and diffusion mechanisms. The dynamic mesh transient model is used to simulate the changes in the geometric shape of the fabric when it moves in the drying box. By dividing the dynamic mesh area and other calculation areas, computing power can be saved. The translational deformation boundary conditions of the geometric model are used to define the movement trajectory and deformation mode of the fabric in the drying box. The external boundary conditions of the drying box are used to set the heat exchange and fluid exchange conditions between the drying box and the outside world. The fabric heat and mass transfer boundary conditions are used to determine the heat and moisture exchange conditions between the fabric surface and the air.

[0020] like Figure 2 As shown, the shaping machine air duct includes an array of two circular air outlets, and the high-temperature airflow is emitted from the shaping machine air duct to the upper and lower surfaces of the wet porous fabric to dry and shape it. In this embodiment, the vertical jet area is used as the simulation calculation area, which includes the fabric model and the vertical area between the upper and lower surfaces of the fabric model and the plane where the air outlet is located. Among them, the vertical distance between the upper and lower surfaces of the fabric model and the plane where the air outlet is located is The diameter of the air outlet is , the high temperature air flow velocity and the injection velocity are , the fabric movement speed is It is worth noting that the air outlet of the shaping machine air duct in this embodiment is circular, but it is not limited to this. When air outlets of other shapes are selected, the parameters Also changed accordingly.

[0021] like Figure 3 As shown, this embodiment divides the calculation area into a dynamic mesh area, a free jet area, and a porous medium area. During simulation calculations, the area of ​​the dynamic mesh area can be reduced to save computing power. At the same time, the dynamic mesh area is extended using a periodic extended boundary, which can effectively characterize the relative displacement of the fabric to ensure the accuracy and stability of the mesh. In addition, when constructing the fabric pore structure model, the method of regular graphic wrapping is used to equate irregular fabric types to rectangles, solving the problem of vertex overlap deformation caused by mesh movement during calculations.

[0022] The flow conservation equation in the control volume unit of the dynamic mesh area is: In the formula, represents the relative offset of the porous fabric, Indicates the speed of the fabric in the jet space. is the deformation speed of the grid, is the diffusion coefficient, is the fluid density, is the flux, is the flux source term, For control unit The borders of and denote the current and next time steps respectively, is the number of planes controlling the unit, Representation plane The area vector of .

[0023] The simulation results are as follows Figure 4 The left figure is the temperature simulation calculation result, which shows the ratio of the air outlet diameter at different vertical distances. , and fabric movement speed The surface temperature of the fabric under the condition of The smaller the fabric, the faster it moves. The larger the value, the lower the fabric surface temperature. The right figure is the humidity simulation calculation result, showing the humidity at different times. , and fabric movement speed The surface humidity of the fabric under the condition of The longer the fabric, the faster it moves. The larger it is, the lower the humidity on the fabric surface.

[0024] In order to verify the simulation results, a corresponding experimental verification device was built to measure the heat and moisture distribution parameters on the fabric surface. Figure 5 As shown, it includes a fresh air inlet 1, a solid desiccant 2, a heater 3, a compressor 4, a static pressure box 5, an air valve 6, an air inlet 7, a temperature, humidity, and wind speed sensor module 8, a drying box 9, a heat preservation cotton 10, a circular air hole 11, a return air outlet 12, a fabric 13, a variable cross-section air duct 14, a connecting pipe 15, an exhaust port 16, a detachable rear plate 17, a tray bracket 18, a pressure transmitter 19, and an air supply box 20. When the equipment is running, the centrifugal fan 4 inhales outdoor air from the fresh air inlet 1 and the temperature rises after passing through the heater 3. The hot air enters the air inlet duct 7 symmetrically distributed up and down in the drying box 9 through the air valve 6. The plug-in temperature and humidity sensor and wind speed sensor assembly module 8 are built in the air inlet duct. After completing the parameter measurement, the variable cross-section air duct 14 entering the drying box is sprayed on the surface of the fabric 13 through the circular air outlet 11 above the air duct. The fabric 13 is placed on the tray support 18, and protruding slide rails are provided on both sides of the oven to ensure the placement and movement of the support. The pressure transmitter 19 is connected to the tray support 18 at the bottom of the fabric. During the drying process, as the moisture inside the fabric evaporates, its mass continues to decrease, thereby outputting the real-time mass change of the fabric. After the drying is completed, a part of the hot air is discharged from the exhaust port 16, and the other part of the hot air flows back to the air supply box 20 after reducing the moisture in the air through the solid desiccant 2 in the circulation pipe through the return air port 12, thereby completing a complete drying cycle.

[0025] More specifically, Figure 6 As shown, at least two air inlets are formed on the side wall of the drying box, each of which is detachably connected to an air duct, a tray bracket is arranged between two adjacent air ducts, and a plurality of air outlets are formed on the side of each air duct facing the tray bracket. The hot air flow is sent from the air inlet into the air duct by the air supply device and then sprayed on the fabric placed on the tray bracket through the air outlet for heat setting. The tray bracket is provided with a slide rail to drive the fabric placed thereon to move along the slide rail during the heat setting process; the tray bracket is connected to a pressure transmitter to detect the mass change of the fabric placed thereon in real time; a sensor module is arranged in the air inlet to measure the temperature, humidity and wind speed of the hot air flow. The surface of the fabric is also arranged with an array of temperature and humidity sensors to detect the heat and humidity distribution on the surface of the fabric.

[0026] like Figure 7As shown in the figure, the air duct is a replaceable device. By adjusting the shape of the air outlet, the air outlet form can be changed and can be used in different types of fabric drying processes. By changing the model and simulation related parameters, it can also be applied to the parameter optimization design of other types of belt conveyor heat and mass transfer processes. This numerical calculation method is universal and extensible.

Claims

1. A method for predicting heat and moisture distribution on the surface of heat-setting process fabric, characterized in that: The following steps are involved: According to the working conditions of the heat setting process, a full-scale model of the drying oven and a model of the fabric pore structure were constructed; Construct fluid turbulence, heat and mass transfer, and dynamic mesh transient models, and conduct multi-physics coupling of heat and moisture transfer between the fabric pore structure model and the full-scale drying oven model; Set the translational deformation and heat and mass transfer boundary conditions of the fabric pore structure model, as well as the external boundary conditions of the full-scale drying oven model; Define the material properties of the fabric pore structure model and the material properties of the air in the full-scale model of the drying oven; The calculation area is set based on the physical field involved in the fabric pore structure model, and the dynamic grid area is delineated in the calculation area, so that the fabric pore structure model moves in the full-size model of the drying box in a specified direction and at a set speed; The calculation area is meshed and the simulation time and step size are set to simulate and obtain the temperature and humidity distribution when the airflow acts on the surface of the fabric pore structure model.

2. The method according to claim 1, characterized in that The calculation area is set as the vertical area between the fabric pore structure model and its upper and lower surfaces and the plane where the air supply outlet is located.

3. The method according to claim 1, characterized in that Before the steps of meshing the computational region and setting the simulation time and step size, the step also includes the steps of demarcating the free jet region and the porous medium region in the computational region.

4. The method according to claim 1, characterized in that: When meshing the fabric pore structure model, free tetrahedral mesh is used.

5. The method according to claim 1, characterized in that Before the step of simulating and obtaining the temperature and humidity distribution of the airflow acting on the surface of the fabric pore structure model, the step of extending the dynamic grid area by using a periodic extended boundary is also included.

6. The method according to claim 1, characterized in that After the step of simulating and obtaining the temperature and humidity distribution of the airflow acting on the surface of the fabric pore structure model, the step also includes constructing a fabric surface heat and humidity distribution measurement device to verify the simulation result.

7. The method according to claim 5, characterized in that The device for measuring heat and moisture distribution on the surface of fabric comprises a drying box, at least two air inlets are formed on the side wall of the drying box, each air inlet is detachably connected with an air duct, a tray bracket is arranged between two adjacent air ducts, and a plurality of air outlets are formed on a side of each air duct facing the tray bracket, a hot air flow is sent into the air duct from the air inlet by an air supply device, and then sprayed onto the fabric placed on the tray bracket through the air outlet for heat setting, a slide rail is arranged on the tray bracket, and the fabric placed thereon is driven to move along the slide rail during the heat setting process; the tray bracket is connected to a pressure transmitter for detecting mass changes of the fabric placed thereon in real time; a sensor module is arranged in the air inlet for measuring the temperature, humidity and wind speed of the hot air flow.

8. The method according to claim 6, characterized in that The plane where each air outlet is located is parallel to the fabric, and the formed air outlet area can completely cover the side of the fabric facing the air duct.

9. The method according to claim 6, characterized in that It also includes a temperature and humidity sensor array for detecting the heat and humidity distribution on the fabric surface.

10. The method according to claim 6, characterized in that A return air port is formed on the upper wall of the drying box away from the air inlet. The return air port is connected to the air supply device through a return air duct. A desiccant is arranged in the return air duct. The hot air in the drying box flows into the return air duct through the return air port and flows back to the air supply device after being dehumidified by the dryer.

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