Measurement and calculation system and method for measuring internal temperature of accumulated dust and heat source position

Abstract

The invention discloses a measuring and calculating system and method for measuring the internal temperature of accumulated dust and the position of a heat source. According to the system, mounting holes are formed in a supporting platform at the upper end of a rack; the heat transfer plate is surrounded by the heat insulation ring and mounted above the mounting hole, a bearing cylinder is mounted on the upper surface, and a heating resistance wire is mounted on the lower surface; the plurality of first thermocouples are arranged at the middle section in the bearing cylinder; a plurality of second thermocouples are mounted on the heat transfer plate; the temperature measuring device is arranged on the periphery of the rack; the thermal image acquisition device is arranged above the bearing cylinder; the method comprises the following steps: establishing a conduction-heat convection model; a discretization equation of a conduction-heat convection model is obtained through a temperature experiment, and inherent characteristic parameters such as heat conduction coefficients of dust are calculated according to different dust; and the temperature and the heat source position in any accumulated dust are measured and determined. The system can reveal the temperature transfer rule in the accumulated dust, and the method can be used for measuring and calculating temperature data and heat source position information in any accumulated dust.

Description

Technical Field

[0001] The invention belongs to the technical field of dust monitoring, and in particular relates to a measuring system and method for measuring the internal temperature and heat source position of accumulated dust. Background Art

[0002] In industrial production, dust accumulation may slowly oxidize. For example, coal and metal dust will generate heat in the oxidation reaction, which will lead to heat accumulation and temperature rise. When the temperature rises to a certain threshold, it will ignite and explode the combustible dust, which will cause serious production safety accidents. At present, industrial dust explosion accidents occur frequently, causing serious personal injury and economic losses. Therefore, monitoring the temperature inside the accumulated dust and locating the position of the heat source inside the dust are extremely important for effectively reducing dust explosion accidents and ensuring production safety. However, the traditional method of monitoring the temperature inside the dust relies on limited thermocouple measurement points, which cannot fully reflect the temperature distribution inside the dust. For this reason, it is urgent to provide a system and method that can measure the three-dimensional temperature field inside the dust in real time and locate the position of the internal heat source. Summary of the invention

[0003] In view of the problems existing in the above-mentioned prior art, the present invention provides a measurement system and method for determining the internal temperature and heat source position of accumulated dust. The system has a simple structure and low manufacturing cost. It can help to reveal the temperature transfer law inside the accumulated dust, and can be helpful in determining the temperature of various parts of the accumulated dust and the position of the internal heat source, which can effectively reduce the probability of dust explosion accidents. The method can efficiently and accurately measure the temperature data at various parts inside any accumulated dust and the internal heat source position information, and can realize scientific monitoring of the temperature data of any accumulated dust.

[0004] In order to achieve the above-mentioned object, the present invention provides a measurement system for measuring the internal temperature of accumulated dust and the position of the heat source, comprising a bottom fixing table, a frame, a heat insulation ring, a heat transfer plate, a bearing cylinder, a heating assembly, a vertical support, a pull wire, a first thermocouple, a second thermocouple, a temperature measuring device, a thermal image acquisition device and a data processing terminal;

[0005] The lower end of the frame is fixedly mounted on the central area of ​​the upper end of the bottom fixed platform, and the upper end thereof has a horizontal support platform, and a mounting hole is opened in the central area of ​​the support platform;

[0006] The diameter of the inner hole of the heat insulation ring is matched with the outer diameter of the mounting hole, the heat insulation ring is fixedly mounted on the support platform, and its inner hole is aligned with the mounting hole;

[0007] The outer diameter of the heat transfer plate matches the inner hole of the heat insulation ring, and the heat transfer plate is fixedly installed in the inner hole of the heat insulation ring;

[0008] The lower opening end of the bearing cylinder is fixedly connected to the upper end face of the heat transfer plate. Two through holes are oppositely formed at the left and right ends of the middle section of the bearing cylinder, and the inside of the bearing cylinder is filled with accumulated dust;

[0009] The heat component includes a heating power supply, a temperature controller, and a heating resistance wire. The heating resistance wire is arranged throughout the lower end face of the heat transfer plate and is connected to the heating power supply through the temperature controller;

[0010] Two vertical support members are distributed oppositely on the left and right sides of the frame, and their lower ends are fixedly connected to the upper end face of the bottom fixing table;

[0011] The wire is horizontally passed through the two through holes on the bearing cylinder, and its two ends are respectively connected to the upper parts of the two vertical support members;

[0012] A plurality of first thermocouples are sequentially spaced along the left-right direction and are installed on the wire. Among them, the two first thermocouples located at the two ends in the left-right direction are respectively connected to the left side wall and the right side wall of the bearing cylinder;

[0013] A plurality of second thermocouples are correspondingly arranged below the plurality of first thermocouples and are closely installed on the upper end face of the heat transfer plate;

[0014] The temperature measuring device is arranged on the periphery of the frame and is used to collect temperature signals in the environment in real time;

[0015] The thermal imaging acquisition device is supported above the bearing cylinder, and its acquisition surface is parallel to the upper surface of the to-be-tested accumulated dust, and is used to generate a temperature image by detecting the infrared radiation of the accumulated dust;

[0016] The data processing terminal is respectively connected to the plurality of first thermocouples, the plurality of second thermocouples, the temperature controller, the temperature measuring device, and the thermal imaging acquisition device.

[0017] Furthermore, in order to endow the vertical support member with elastic support capacity and at the same time facilitate the adjustment of the support height, the vertical support member includes a lower support column, a middle connecting spring, an upper support column, a height adjustment sleeve and a connecting ear plate. The lower end of the lower support column is fixedly connected to the upper end of the bottom fixed platform. The lower end of the middle connecting spring is fixedly connected to the upper end of the lower support column. The outer thread structure is disposed all over the column body of the upper support column, and its lower end is fixedly connected to the upper end of the middle connecting spring. The inner diameter of the height adjustment sleeve is adapted to the outer diameter of the upper support column, and an inner thread structure is provided inside corresponding to the outer thread structure, and it is sleeved outside the upper support column through thread fit. The outer end of the connecting ear plate is fixedly connected to one side of the upper part of the height adjustment sleeve, a wire passing hole is provided at its inner end, and it is connected to the pulling wire through the wire passing hole. In order to facilitate the manual adjustment of the height of the height adjustment sleeve, an adjustment handle can also be fixedly connected to the upper end of the height adjustment sleeve.

[0018] Furthermore, in order to ensure the accuracy of the measurement and at the same time ensure the high efficiency of heat transfer, the carrier cylinder and the heat transfer plate are made of the same material, both of which are made of metal heat transfer materials.

[0019] As a preference, the data processing terminal is an industrial computer.

[0020] In the present invention, an installation hole is provided at the center of the support platform. Meanwhile, a heat transfer plate is fixedly installed in the area where the installation hole is located by using a heat insulation ring. On this basis, heating resistance wires are laid all over the lower surface of the heat transfer plate. In this way, only the heat transfer plate can be efficiently heated during heating, ensuring the efficiency of heating. At the same time, it can ensure that the heat on the heat transfer plate will not be transferred to surrounding objects, ensuring the stability of the heat on the heat transfer plate and the bearing cylinder, which is beneficial to ensuring the accuracy of test data, and further can help obtain an accurate heat conduction - heat convection model. Connect the heating resistance wires to the heating power supply through a temperature controller, which can facilitate using the temperature controller to control the on - off action of the heating resistance wires. At the same time, it can facilitate using the temperature controller to control the heating temperature range of the heating resistance wires. Two through - holes are provided on the left and right opposite sides in the middle section of the bearing cylinder. Meanwhile, two vertical support members are installed on the left and right sides of the frame. Then, the pull wire passes through the two through - holes and is connected to the two vertical support members, so that the pull wire can be stably supported in the middle section of the bearing cylinder. Thus, it can facilitate using the pull wire to provide an installation basis for multiple first thermocouples. In this way, after the inside of the bearing cylinder is filled with dust, it is convenient to effectively monitor the temperatures at different positions inside the accumulated dust by using multiple first thermocouples. In addition, connecting the two first thermocouples at both ends in the left - right direction to the left - hand side wall and the right - hand side wall of the bearing cylinder respectively can ensure that these two first thermocouples can effectively monitor the temperatures at the side edges of the accumulated dust. Multiple second thermocouples are installed on the heat transfer plate corresponding to the multiple first thermocouples in the inner area of the bearing cylinder. After the inside of the bearing cylinder is filled with dust, it is convenient to effectively monitor the temperature of the lower surface of the accumulated dust by using multiple second thermocouples. By setting a temperature acquisition device around the frame, it is convenient to monitor the temperature data in the environment in real time. By setting a thermal imaging acquisition device above the bearing cylinder, it is convenient to collect the thermal image of the upper surface of the accumulated dust in real time, which is conducive to obtaining the temperature data of the upper surface of the accumulated dust. Through the coordinated setting of the first thermocouples, the second thermocouples, the temperature acquisition device and the thermal imaging acquisition device, combined with the temperature conduction theory, the temperature conduction test can be completed. At the same time, it is beneficial to obtain a definite heat conduction - heat convection model, and further can provide reliable technical support for the reliable monitoring of the temperature inside any accumulated dust and the positioning of the heat source location.

[0021] The system has a simple structure and low manufacturing cost. It can help reveal the temperature transfer law inside the accumulated dust and is beneficial to determining the temperature at each part of the accumulated dust and the location of the internal heat source, thereby effectively reducing the probability of dust explosion accidents and greatly improving the safety factor of production operations.

[0022] The present invention also provides a method for measuring the temperature and heat source location inside the accumulated dust. Using a measurement system for measuring the temperature and heat source location inside the accumulated dust, it includes the following steps:

[0023] Step 1: Construct the theoretical equation of the heat conduction - heat convection model;

[0024] S11: Establish the heat conduction model inside the accumulated dust according to formula (1);

[0025]

[0026] In the formula, T is the temperature, t is the time, α is the thermal diffusivity, and g(x, y, z, t) is the heat generation rate of the internal heat source per unit volume;

[0027] S12: Construct the heat convection model between the dust surface and the air;

[0028] S12 - 1: For the upper surface of the accumulated dust, establish the convective heat transfer boundary condition according to formula (2);

[0029]

[0030] In the formula, is the derivative of the temperature in the normal direction of the boundary, k is the thermal conductivity, h is the convective heat transfer coefficient, and T air is the air temperature;

[0031] S12 - 2: For the lower surface and the side surface of the accumulated dust, their temperatures are the same as those of the bearing cylinder (5);

[0032] Step 2: Use the finite difference method to determine the parameters in the heat conduction - heat convection model;

[0033] S21: Discretize the accumulated dust in the bearing cylinder into a three - dimensional grid. Among them, in the radial r direction, from the center of the ring r = 0 to the edge of the ring r = R, the step size is Δr; in the angular θ direction, from 0 to 2π, the step size is Δθ; in the axial z direction, from the bottom of the dust z = 0 to the top of the dust z = H, the step size is Δz;

[0034] S22: Discretization of the heat conduction model; Based on the heat conduction equation in the cylindrical coordinate system, discretize formula (1) to obtain the discretized equation of the heat conduction model, as shown in formula (3);

[0035]

[0036] In the formula, represents the temperature of the grid point (r i , θ j , z k ) at the nth time step; Δt is the time step; Δr, Δθ, and Δz are the grid step sizes in the radial, angular, and axial directions respectively;

[0037] S23: Discretization of the heat convection model to obtain the discretized equation of the heat convection model;

[0038] S23-1: For the upper surface of the accumulated dust, discretize formula (2) to obtain the discretized equation of the upper boundary heat convection model, as shown in formula (4);

[0039]

[0040] where N Z is the grid index of the upper surface of the dust;

[0041] S23-2: For the lower surface and the side surface of the accumulated dust, obtain the discretized equations of the lower boundary and side surface heat convection models according to formula (5) and formula (6) respectively;

[0042]

[0043] where T plate is the temperature of the bearing cylinder, and N r is the radial grid index of the edge of the bearing cylinder;

[0044] S24: Conduct a standard temperature hot plate experiment on the accumulated dust, and collect the dust surface temperature data and the temperature data of several monitoring points inside the dust;

[0045] S24-1: Line the inside of the bearing cylinder with the dust to be measured, and ensure that the thickness of the dust layer is uniform everywhere inside the bearing cylinder to form the accumulated dust to be measured;

[0046] S24-2: Control the temperature controller to start working through the data processing terminal, so that the heating power supply supplies power to the heating resistance wire. At the same time, use the temperature controller to control the heating temperature of the heating resistance wire, so that the temperature of the heat transfer plate is kept constant within the preset temperature range;

[0047] Use multiple first thermocouples located in the middle section of the bearing cylinder to collect the first temperature signals inside the dust layer in real time and send them to the data processing terminal. Use multiple second thermocouples located at the bottom of the bearing cylinder to collect the second temperature signals on the surface of the heat transfer plate in real time and send them to the data processing terminal. Use the temperature measuring device to collect the ambient temperature signal in real time and send it to the data processing terminal. The data processing terminal obtains the first temperature data, the second temperature data and the ambient temperature data according to the first temperature signal and the second temperature signal respectively;

[0048] At the same time, use the thermal imaging acquisition device to detect the infrared radiation of the accumulated dust in real time and generate a temperature image, and then send the temperature image to the data processing terminal. The data processing terminal obtains the upper surface temperature data of the dust according to the temperature image;

[0049] S24-3: The data processing terminal divides the obtained multiple first temperature data and multiple second temperature data according to the position information of multiple first thermocouples and the position information of multiple second thermocouples 4, respectively obtaining the internal temperature data, side temperature data, and lower surface temperature data of the accumulated dust;

[0050] S25: Conduct numerical calculations of the temperature conduction theory; input the obtained internal temperature data into the discretized equation of the heat conduction model, and use the obtained upper surface temperature data, side temperature data, and lower surface temperature data as boundary conditions and input them into the discretized equation of the heat convection model. By calculation, determine the thermal conductivity k, convective heat transfer coefficient h, and thermal diffusivity α for the dust to be measured, and further obtain the discretized equation of the heat conduction model and the discretized equation of the heat convection model for the dust to be measured;

[0051] Step 3: Calculate the internal temperature of any accumulated dust and determine the position of the internal heat source;

[0052] S31: Install multiple temperature sensors at key points inside any accumulated dust;

[0053] S32: Use a laser scanner to scan any accumulated dust to obtain the three-dimensional surface data of the accumulated dust, and send the three-dimensional surface data to the data processing terminal; the data processing terminal generates a three-dimensional geometric model of the accumulated dust based on the three-dimensional surface data, and discretizes the three-dimensional shape of the accumulated dust into a finite element network or a finite difference network to obtain the three-dimensional grid of the accumulated dust, and determine the coordinates (i, j, k) of each point;

[0054] S33: Use an infrared thermal imager to photograph the temperature distribution on the surface of any accumulated dust, and send the temperature data on the surface of the accumulated dust to the data processing terminal; use the temperature sensors to collect the key point temperature signals in real time and send them to the data processing terminal, and the data processing terminal obtains the key point temperature data according to the key point temperature signals;

[0055] S34: Fix the temperature of the grid points on the outer surface of the three-dimensional grid to the known value T according to the temperature data on the surface of any accumulated dust boundary ;

[0056] S35: Substitute the key point temperature data into the discretized equation of the heat conduction model to establish the Laplace equation, as shown in formula (7);

[0057]

[0058] S36: Solve formula (7) to obtain the temperatures at various locations inside any accumulated dust, inversely fit and calculate the heat source positions inside any accumulated dust, establish a three-dimensional temperature field of the accumulated dust based on the temperature data at various locations inside and the heat source position information inside, and then output the temperature data at various locations inside, the heat source position information inside, and the three-dimensional temperature field to a visualization terminal, and perform real-time display of the temperature data at various locations inside, the heat position information inside, and the three-dimensional temperature field through the visualization terminal.

[0059] As an optimization, in S12 of step one, the discretized network is a hexahedron or a tetrahedron.

[0060] As an optimization, in S36 of step three, the thermodynamic iteration method or an efficient algorithm is used to calculate the temperature at any internal point.

[0061] As an optimization, in S36 of step three, the visualization terminal performs real-time display in the form of a thermal imaging map or a three-dimensional temperature cloud map.

[0062] The present invention provides a method for real-time calculation of the three-dimensional temperature field of accumulated dust based on experimental data and a heat conduction - heat convection model. First, the theoretical equation of the heat conduction - heat convection model is constructed. Then, through the finite difference method combined with the standard temperature hot plate experiment, the thermal conductivity k, the convective heat transfer coefficient h, and the thermal diffusivity α for the current dust to be measured are determined. Since the thermal conductivity k, the convective heat transfer coefficient h, and the thermal diffusivity α are related to the substance itself, the composition, structure, density, temperature, humidity, etc. of different substances will affect the specific values of the above coefficients. Therefore, before monitoring the temperature of any accumulated dust, first determine the thermal conductivity k, the convective heat transfer coefficient h, and the thermal diffusivity α of the current dust to be measured through the standard temperature hot plate experiment. In this way, the discretized equation of the heat conduction model and the discretized equation of the heat convection model applicable to the current dust to be measured can be obtained, ensuring more accurate and efficient monitoring of the temperature of any accumulated dust in the subsequent process. Then, based on the key point temperature data obtained by the temperature sensors buried at the key points inside any accumulated dust and the temperature distribution on the surface of any accumulated dust obtained by using an infrared thermal imager, the Laplace equation can be constructed by combining the discretized equation of the heat conduction model. By solving the Laplace equation, the temperature distribution at any point inside any accumulated dust can be deduced. In this way, the temperature data at various locations inside any accumulated dust can be measured efficiently and accurately. At the same time, the heat source positions inside any accumulated dust can be inversely fitted and calculated, and a three-dimensional temperature field of the accumulated dust is established based on the temperature data at various locations inside and the heat source position information inside, so as to realize scientific monitoring of the temperature data of any accumulated dust, thereby effectively reducing the probability of dust explosion accidents and greatly improving the safety factor of production operations. Description of the Drawings

[0063] Figure 1 is a schematic structural diagram of the measurement system in the present invention;

[0064] Figure 2 is Figure 1 the top view of

[0065] Figure 3 is a schematic block diagram of the circuit principle part in the present invention.

[0066] In the figure: 1. Heat insulation ring, 2. Heat transfer plate, 3. First thermocouple, 4. Second thermocouple, 5. Bearing cylinder, 6. Heating resistance wire, 7. Thermal imaging acquisition device, 8. Temperature measurement device, 9. Bottom fixing platform, 10. Vertical support member, 11. Lower support column, 12. Middle section connecting spring, 13. Upper support column, 14. Connecting ear plate, 15. Frame, 16. Support platform, 17. Pulling wire, 18. Height adjusting sleeve. Specific embodiments

[0067] The present invention will be further described below.

[0068] As Figures 1 to 3 shown, the present invention provides a measurement system for measuring the internal temperature and heat source position of accumulated dust, including a bottom fixing platform 9, a frame 15, a heat insulation ring 1, a heat transfer plate 2, a bearing cylinder 5, a heating assembly, a vertical support member 10, a pulling wire 17, a first thermocouple 3, a second thermocouple 4, a temperature measurement device 8, a thermal imaging acquisition device 7 and a data processing terminal;

[0069] The lower end of the frame 15 is fixedly installed in the central area of the upper end of the bottom fixing platform 9, and its upper end has a horizontal support platform 16, and an installation hole is provided in the central area of the support platform 16;

[0070] The inner diameter of the heat insulation ring 1 is adapted to the outer diameter of the installation hole, the heat insulation ring 1 is fixedly installed on the support platform 16, and its inner hole is aligned with the installation hole;

[0071] The outer diameter of the heat transfer plate 2 is adapted to the inner diameter of the heat insulation ring 1, and the heat transfer plate 2 is fixedly installed in the inner hole of the heat insulation ring 1;

[0072] The lower open end of the bearing cylinder 5 is fixedly connected to the upper end surface of the heat transfer plate 2, two through holes are oppositely provided at the left and right ends of the middle section of the bearing cylinder 5, and the inside of the bearing cylinder 5 is filled with accumulated dust;

[0073] The heating assembly includes a heating power supply, a temperature controller and a heating resistance wire 6, the heating resistance wire 6 is arranged all over the lower end surface of the heat transfer plate 2 and is connected to the heating power supply through the temperature controller;

[0074] Two vertical support members 10 are distributed relatively to the left and right on the left and right sides of the frame 15, and their lower ends are fixedly connected to the upper end surface of the bottom fixed platform 9;

[0075] The wire 17 is horizontally threaded through two through holes on the bearing cylinder 5, and its two ends are respectively connected to the upper parts of the two vertical support members 10;

[0076] A plurality of first thermocouples 3 are sequentially spaced along the left-right direction and distributed inside the bearing cylinder 5, and are installed on the wire 17. Among them, the two first thermocouples 3 located at both ends in the left-right direction are respectively connected to the left side wall and the right side wall of the bearing cylinder 5;

[0077] A plurality of second thermocouples 4 are correspondingly arranged below the plurality of first thermocouples 3, and are fittingly installed on the upper end surface of the heat transfer plate 2;

[0078] The temperature measuring device 8 is arranged on the periphery of the frame 15 and is used to collect temperature signals in the environment in real time;

[0079] The thermal imaging acquisition device 7 is supported above the bearing cylinder 5, and its acquisition surface is parallel to the upper surface of the to-be-measured accumulated dust, and is used to generate a temperature image by detecting the infrared radiation of the accumulated dust;

[0080] The data processing terminal is respectively connected to the plurality of first thermocouples 3, the plurality of second thermocouples 4, the temperature controller, the temperature measuring device 8 and the thermal imaging acquisition device 7.

[0081] In order to endow the vertical support member with elastic support ability, and at the same time, in order to facilitate the adjustment of the support height, the vertical support member 10 includes a lower support column 11, a middle section connecting spring 12, an upper support column 13, a height adjustment sleeve 18 and a connecting ear plate 14. The lower end of the lower support column 11 is fixedly connected to the upper end of the bottom fixed platform 9. The lower end of the middle section connecting spring 12 is fixedly connected to the upper end of the lower support column 11. The upper support column 13 is provided with an external thread structure over the entire column body, and its lower end is fixedly connected to the upper end of the middle section connecting spring 12. The inner diameter of the height adjustment sleeve 18 is adapted to the outer diameter of the upper support column 13, and an internal thread structure is correspondingly provided inside it and is sleeved outside the upper support column 13 through thread fit; the outer end of the connecting ear plate 14 is fixedly connected to one side of the upper part of the height adjustment sleeve 18, and a wire passing hole is opened at its inner end and is connected to the wire 17 through the wire passing hole. In order to facilitate the manual adjustment of the height of the height adjustment sleeve 18, an adjustment handle can also be fixedly connected to the upper end of the height adjustment sleeve 18.

[0082] In order to ensure the measurement accuracy, and at the same time, in order to ensure the high efficiency of heat transfer, the bearing cylinder 5 and the heat transfer plate 2 are made of the same material, both made of a metal heat transfer material.

[0083] As an optimization, the data processing terminal is an industrial computer.

[0084] In the present invention, an installation hole is opened at the center of the support platform. Meanwhile, a heat transfer plate is fixedly installed in the area where the installation hole is located by using a heat insulation ring. On this basis, heating resistance wires are laid all over the lower surface of the heat transfer plate. In this way, only the heat transfer plate can be efficiently heated during heating, ensuring the efficiency of heating. At the same time, it can ensure that the heat on the heat transfer plate will not be transferred to surrounding objects, ensuring the stability of the heat on the heat transfer plate and the bearing cylinder, which is beneficial to ensuring the accuracy of test data, and further helps to obtain an accurate heat conduction - heat convection model. Connect the heating resistance wires to the heating power supply through a temperature controller, which can facilitate the use of the temperature controller to control the on - off action of the heating resistance wires. At the same time, it can facilitate the use of the temperature controller to control the heating temperature range of the heating resistance wires. Two through - holes are opened on the left and right opposite sides in the middle section of the bearing cylinder. Meanwhile, two vertical support members are installed on the left and right sides of the frame. Then, the pull wire passes through the two through - holes and is connected to the two vertical support members, so that the pull wire can be stably supported in the middle section of the bearing cylinder. Thus, it can facilitate the use of the pull wire to provide an installation basis for multiple first thermocouples. In this way, after the inside of the bearing cylinder is filled with dust, it is convenient to use multiple first thermocouples to effectively monitor the temperatures at different positions inside the accumulated dust. In addition, the two first thermocouples located at both ends in the left - right direction are respectively connected to the left side wall and the right side wall of the bearing cylinder, which can ensure that these two first thermocouples can effectively monitor the temperatures at the side edges of the accumulated dust. A plurality of second thermocouples are installed on the heat transfer plate corresponding to the multiple first thermocouples in the internal area of the bearing cylinder. After the inside of the bearing cylinder is filled with dust, it is convenient to use multiple second thermocouples to effectively monitor the temperature of the lower surface of the accumulated dust. By setting a temperature acquisition device outside the frame, it is convenient to monitor the temperature data in the environment in real time. By setting a thermal imaging acquisition device above the bearing cylinder, it is convenient to collect the thermal image of the upper surface of the accumulated dust in real time, which is beneficial to obtaining the temperature data of the upper surface of the accumulated dust. Through the coordinated setting of the first thermocouples, the second thermocouples, the temperature acquisition device and the thermal imaging acquisition device, combined with the temperature conduction theory, the temperature conduction test can be completed. At the same time, it is beneficial to obtain a definite heat conduction - heat convection model, which can provide reliable technical support for the reliable monitoring of the temperature inside any accumulated dust and the positioning of the heat source location.

[0085] This system has a simple structure and low manufacturing cost. It can help to reveal the temperature transfer law inside the accumulated dust, and is beneficial to determining the temperature at each part of the accumulated dust and the location of the internal heat source, thereby effectively reducing the probability of dust explosion accidents and greatly improving the safety factor of production operations.

[0086] The present invention also provides a method for measuring the internal temperature and heat source position of accumulated dust, using a measurement system for measuring the internal temperature and heat source position of accumulated dust, comprising the following steps:

[0087] Step 1: Construct the theoretical equation of the heat conduction - heat convection model;

[0088] S11: Based on Fourier's law of heat conduction and the law of conservation of energy, establish the heat conduction model inside the accumulated dust according to formula (1);

[0089]

[0090] In the formula, T is the temperature, t is the time, α is the thermal diffusivity, k is the thermal conductivity, c is the specific heat capacity, ρ is the density, and g(x, y, z, t) is the heat generation rate of the internal heat source per unit volume;

[0091] Since the given situation is the accumulation of dust of a certain substance, the calculation of the thermal conductivity k is relatively complex. For example, when given the dust to be measured (such as silica dust), the equivalent thermal conductivity during dust accumulation is the result of the combined action of dust particles and air gaps, and can be simply estimated as: where k air is the thermal conductivity of air, approximately 0.026; is the thermal conductivity of silica (amorphous silica is about 1.4), and φ is the bulk density of the dust (i.e., the proportion of the dust volume in the total volume);

[0092] S12: Construct the heat convection model between the dust surface and air;

[0093] S12 - 1: When the upper surface of the accumulated dust contacts the air, convective heat transfer will occur. For the upper surface of the accumulated dust, establish the convective heat transfer boundary condition according to formula (2);

[0094]

[0095] In the formula, is the derivative of the temperature in the normal direction of the boundary, h is the convective heat transfer coefficient, and T air is the air temperature;

[0096] In particular, when calculating the heat conduction of the dust and the convective heat transfer between its upper surface and the air, the Biot number Bi can be calculated to simplify the calculation, where, Let \(V\) be the volume of the accumulated dust and \(A\) be the surface area of the accumulated dust in contact with the air. If \(Bi \lt 0.1\), it indicates that the thermal conductivity inside the solid is extremely small, and the heat conduction process inside the solid does not need to be considered. Only the convective heat transfer between the solid and the air needs to be considered. If \(Bi \gt\gt 0.1\), it indicates that the internal thermal resistance of the object is equivalent to or greater than the external thermal resistance, and the internal temperature gradient cannot be ignored. The heat conduction inside the dust and the convective heat transfer of its surface to the air need to be considered simultaneously.

[0097] S12 - 2: For the lower surface and side surfaces of the accumulated dust, since the lower surface and side surfaces of the accumulated dust are in good contact with the bearing cylinder 5 and the thermal resistance can be ignored, the temperatures of the lower surface and side surfaces of the accumulated dust and the bearing cylinder 5 are the same;

[0098] Step 2: Use the finite difference method to determine the parameters in the heat conduction - heat convection model;

[0099] S21: Discretize the accumulated dust in the bearing cylinder 5 into a three - dimensional grid, and each grid point corresponds to a temperature value. The grid division should be fine enough to ensure the calculation accuracy. Among them, in the radial \(r\) direction, from the center of the ring \(r = 0\) to the edge of the ring \(r = R\), the step size is \(\Delta r\); in the angular \(\theta\) direction, from \(0\) to \(2\pi\), the step size is \(\Delta \theta\); in the axial \(z\) direction, from the bottom of the dust \(z = 0\) to the top of the dust \(z = H\), the step size is \(\Delta z\);

[0100] S22: Discretization of the heat conduction model; Based on the heat conduction equation in the cylindrical coordinate system, discretize formula (1) to obtain the discretized equation of the heat conduction model, as shown in formula (3);

[0101]

[0102] In the formula, represents the temperature of the grid point \((r\) i ,\theta\) j ,z\) k ) at the \(n\) - th time step; \(\Delta t\) is the time step; \(\Delta r\), \(\Delta \theta\), \(\Delta z\) are the grid step sizes in the radial, angular, and axial directions respectively;

[0103] S23: Discretization of the heat convection model to obtain the discretized equation of the heat convection model;

[0104] S23 - 1: For the upper surface of the accumulated dust, discretize formula (2) to obtain the discretized equation of the upper - boundary heat convection model, as shown in formula (4);

[0105]

[0106] In the formula, \(N\) Z is the grid index of the upper surface of the dust;

[0107] S23-2: For the lower surface and side surfaces of the accumulated dust, the discretization equations of the lower boundary and side surface heat convection models are obtained according to Equation (5) and Equation (6) respectively;

[0108]

[0109] In the formula, T plate is the temperature of the bearing cylinder 5, and N r is the radial grid index at the edge of the bearing cylinder 5;

[0110] S24: Conduct a standard temperature hot plate experiment on the accumulated dust, and collect the dust surface temperature data and the temperature data of several monitoring points inside the dust;

[0111] S24-1: Line the inside of the bearing cylinder 5 with the dust to be measured, and ensure that the thickness of the dust layer is uniform everywhere inside the bearing cylinder 5 to form the accumulated dust to be measured;

[0112] S24-2: Control the temperature controller to start working through the data processing terminal, so that the heating power supply supplies power to the heating resistance wire 6. At the same time, use the temperature controller to control the heating temperature of the heating resistance wire 6 to keep the temperature of the heat transfer plate 2 constant within the preset temperature range;

[0113] Use multiple first thermocouples 3 located in the middle section of the bearing cylinder 5 to collect the first temperature signals inside the dust layer in real time and send them to the data processing terminal. Use multiple second thermocouples 4 located at the bottom of the bearing cylinder 5 to collect the second temperature signals on the surface of the heat transfer plate 2 in real time and send them to the data processing terminal. Use the temperature measuring device 8 to collect the ambient temperature signal in real time and send it to the data processing terminal. The data processing terminal obtains the first temperature data, the second temperature data and the ambient temperature data according to the first temperature signal and the second temperature signal respectively;

[0114] At the same time, use the thermal imaging acquisition device 7 to detect the infrared radiation of the accumulated dust in real time, generate a temperature image, and then send the temperature image to the data processing terminal. The data processing terminal obtains the upper surface temperature data of the dust according to the temperature image;

[0115] S24-3: The data processing terminal divides the obtained multiple first temperature data and multiple second temperature data according to the position information of the multiple first thermocouples 3 and the position information of the multiple second thermocouples 4 to obtain the internal temperature data, the side surface temperature data and the lower surface temperature data of the accumulated dust respectively;

[0116] S25: Conduct numerical calculations of the temperature conduction theory; input the obtained internal temperature data into the discretized equation of the heat conduction model, and input the obtained upper surface temperature data, side surface temperature data, and lower surface temperature data as boundary conditions into the discretized equation of the heat convection model. Determine the thermal conductivity k, convective heat transfer coefficient h, and thermal diffusivity α for the dust to be measured through calculation, and then obtain the discretized equation of the heat conduction model and the discretized equation of the heat convection model for the dust to be measured;

[0117] Step 3: Calculate the internal temperature of any accumulated dust and determine the position of the internal heat source;

[0118] S31: Install multiple temperature sensors at key points inside any accumulated dust;

[0119] S32: Use a laser scanner to scan any accumulated dust to obtain the three-dimensional surface data of the accumulated dust, and send the three-dimensional surface data to the data processing terminal; the data processing terminal generates a three-dimensional geometric model of the accumulated dust based on the three-dimensional surface data, discretizes the three-dimensional shape of the accumulated dust into a finite element network or a finite difference network to obtain the three-dimensional grid of the accumulated dust, and determines the coordinates (i, j, k) of each point;

[0120] S33: Use an infrared thermal imager to photograph the temperature distribution on the surface of any accumulated dust and send the temperature data on the surface of the accumulated dust to the data processing terminal; use the temperature sensors to collect the key point temperature signals in real time and send them to the data processing terminal, and the data processing terminal obtains the key point temperature data based on the key point temperature signals;

[0121] S34: Fix the temperature of the grid points on the outer surface in the three-dimensional grid to the known value T according to the temperature data on the surface of any accumulated dust boundary ;

[0122] S35: Substitute the key point temperature data into the discretized equation of the heat conduction model to establish the Laplace equation as shown in formula (7);

[0123]

[0124] S36: Solve formula (7) to obtain the temperatures at various positions inside any accumulated dust, and inversely fit and calculate the position of the heat source inside the accumulated dust. Based on the temperature data at various positions inside and the heat source position information inside, establish a three-dimensional temperature field of the accumulated dust, and then output the temperature data at various positions inside, the heat source position information inside, and the three-dimensional temperature field to the visualization terminal, and perform real-time display of the temperature data at various positions inside, the internal heat position information, and the three-dimensional temperature field through the visualization terminal.

[0125] As a preference, in step 1 S12, the discretized network is a hexahedron or a tetrahedron.

[0126] As a preference, in step 3 S36, a thermodynamic iteration method or an efficient algorithm is used to calculate the temperature of any internal point. As a preference, the efficient algorithm uses a fast Fourier transform (FFT) or a diagonalization algorithm.

[0127] As a preferred embodiment, in step three S36, the visualization terminal performs real-time display in the form of thermal imaging images or three-dimensional temperature cloud images.

[0128] The present invention provides a real-time calculation method for the three-dimensional temperature field of accumulated dust based on experimental data and a heat conduction-heat convection model. First, a theoretical equation of the heat conduction-heat convection model is constructed. Then, the thermal conductivity k, the convective heat transfer coefficient h and the thermal diffusion coefficient α of the dust to be tested are determined by the finite difference method combined with a standard temperature hot plate experiment. Since the thermal conductivity k, the convective heat transfer coefficient h and the thermal diffusion coefficient α are related to the substance itself, the composition, structure, density, temperature, humidity and the like of different substances will affect the specific values ​​of the above coefficients. Therefore, before temperature monitoring of any accumulated dust, the thermal conductivity k, the convective heat transfer coefficient h and the thermal diffusion coefficient α of the dust to be tested are first determined by a standard temperature hot plate experiment. In this way, the discretized equations of the heat conduction model and the discretized equations of the thermal convection model suitable for the dust to be tested can be obtained, ensuring that any accumulated dust can be subsequently monitored. The temperature of the dust can be monitored more accurately and efficiently. Then, based on the key point temperature data obtained by the temperature sensors buried at the key points inside any accumulated dust, and the temperature distribution on the surface of any accumulated dust obtained by the infrared thermal imager, the Laplace equation can be constructed in combination with the discretized equation of the heat conduction model. By solving the Laplace equation, the temperature distribution of any point inside any accumulated dust can be derived. In this way, the temperature data at various locations inside any accumulated dust can be efficiently and accurately measured. At the same time, the position of the heat source inside any accumulated dust can be calculated by reverse fitting, and the three-dimensional temperature field of the accumulated dust can be established based on the temperature data at various locations inside and the internal heat source position information, so as to realize scientific monitoring of the temperature data of any accumulated dust, thereby effectively reducing the probability of dust explosion accidents and greatly improving the safety factor of production operations.

Claims

1. A measuring system for measuring the internal temperature of accumulated dust and the location of heat sources, comprising a bottom fixing table (9), characterized in that: It also includes a frame (15), a heat insulation ring (1), a heat transfer plate (2), a bearing tube (5), a heating component, a vertical support member (10), a pull wire (17), a first thermocouple (3), a second thermocouple (4), a temperature measuring device (8), a thermal image acquisition device (7) and a data processing terminal; The lower end of the frame (15) is fixedly mounted on the central area of ​​the upper end of the bottom fixing platform (9), and the upper end thereof is provided with a horizontal support platform (16), and a mounting hole is opened in the central area of ​​the support platform (16); The diameter of the inner hole of the heat-insulating ring (1) matches the outer diameter of the mounting hole; the heat-insulating ring (1) is fixedly mounted on the supporting platform (16), and its inner hole is aligned with the mounting hole; The outer diameter of the heat transfer plate (2) matches the inner diameter of the heat insulation ring (1), and the heat transfer plate (2) is fixedly installed in the inner hole of the heat insulation ring (1); The lower open end of the bearing tube (5) is fixedly connected to the upper end surface of the heat transfer plate (2), and two through holes are oppositely formed at the left and right ends of the middle section of the bearing tube (5), and the interior of the bearing tube (5) is filled with accumulated dust; The thermal component comprises a heating power supply, a temperature controller and a heating resistance wire (6), wherein the heating resistance wire (6) is distributed on the lower end surface of the heat transfer plate (2) and is connected to the heating power supply through the temperature controller; Two vertical support members (10) are relatively distributed on the left and right sides of the frame (15), and the lower ends of the two vertical support members (10) are fixedly connected to the upper end surface of the bottom fixing platform (9); The pull wire (17) is transversely passed through two through holes on the bearing tube (5), and its two ends are respectively connected to the upper parts of the two vertical support members (10); A plurality of first thermocouples (3) are sequentially spaced apart inside the support tube (5) along the left-right direction and mounted on the pull wire (17), wherein two first thermocouples (3) located at both ends in the left-right direction are respectively connected to the left side wall and the right side wall of the support tube (5); The plurality of second thermocouples (4) are correspondingly arranged below the plurality of first thermocouples (3) and are fittedly mounted on the upper end surface of the heat transfer plate (2); The temperature measuring device (8) is arranged on the periphery of the frame (15) and is used to collect temperature signals in the environment in real time; The thermal image acquisition device (7) is supported above the supporting tube (5), and its acquisition surface is parallel to the upper surface of the accumulated dust to be measured, and is used to generate a temperature image by detecting the infrared radiation of the accumulated dust; The data processing terminal is respectively connected to a plurality of first thermocouples (3), a plurality of second thermocouples (4), a temperature controller, a temperature measuring device (8) and a thermal image acquisition device (7).

2. A measuring system for measuring the internal temperature of accumulated dust and the location of heat sources according to claim 1, characterized in that: The vertical support member (10) comprises a lower support column (11), a middle connecting spring (12), an upper support column (13), a height adjustment sleeve (18) and a connecting ear plate (14); the lower end of the lower support column (11) is fixedly connected to the upper end of the bottom fixed platform (9); the lower end of the middle connecting spring (12) is fixedly connected to the upper end of the lower support column (11); the upper support column (13) is provided with an external thread structure throughout the column body, and its lower end is fixedly connected to the upper end of the middle connecting spring (12); the inner diameter of the height adjustment sleeve (18) is matched with the outer diameter of the upper support column (13), and an internal thread structure is provided inside thereof corresponding to the external thread structure, and is sleeved on the outside of the upper support column (13) through thread matching; the outer end of the connecting ear plate (14) is fixedly connected to one side of the upper part of the height adjustment sleeve (18), and a wire passing hole is provided at its inner end, and is connected to the pull wire (17) through the wire passing hole.

3. A measuring system for measuring the internal temperature of accumulated dust and the location of heat source according to claim 1 or 2, characterized in that: The supporting tube (5) and the heat transfer plate (2) are made of the same material, both of which are made of metal heat transfer material.

4. A measuring system for measuring the internal temperature of accumulated dust and the location of heat source according to claim 3, characterized in that: The data processing terminal is an industrial computer.

5. A method for measuring the internal temperature of accumulated dust and the location of a heat source, using a measuring system for measuring the internal temperature of accumulated dust and the location of a heat source as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: Construct the theoretical equation of heat conduction-convection model; S11: Establish a heat conduction model inside the accumulated dust according to formula (1); Where T is temperature, t is time, α is the thermal diffusion coefficient, and g(x,y,z,t) is the heat generation rate of the internal heat source per unit volume; S12: Construct a thermal convection model between dust surface and air; S12-1: For the upper surface of the accumulated dust, establish the convective heat transfer boundary condition according to formula (2); In the formula, is the derivative of temperature in the direction of the boundary normal, k is the thermal conductivity, h is the convection heat transfer coefficient, T air is the air temperature; S12-2: The temperature of the lower surface and the side surface of the accumulated dust is the same as that of the carrier tube (5); Step 2: Determine the parameters of the heat conduction-convection model using the finite difference method; S21: discretizing the accumulated dust in the bearing cylinder (5) into a three-dimensional grid, wherein in the radial direction r, from the center of the ring r=0 to the edge of the ring r=R, the step length is Δr; in the angular direction θ, from 0 to 2π, the step length is Δθ; in the axial direction z, from the bottom of the dust z=0 to the top of the dust z=H, the step length is Δz; S22: Discretization of the heat conduction model: Based on the heat conduction equation in the cylindrical coordinate system, formula (1) is discretized to obtain the discretization equation of the heat conduction model, as shown in formula (3); In the formula, represents the nth time step grid point (r i ,θ j ,z k ) temperature; Δt is the time step; Δr, Δθ, Δz are the mesh steps in radial, angular and axial directions respectively; S23: discretization of the thermal convection model, obtaining the discretization equation of the thermal convection model; S23-1: For the upper surface of the accumulated dust, formula (2) is discretized to obtain the discretized equation of the upper boundary thermal convection model, as shown in formula (4); Where N Z is the grid index of the dust upper surface; S23-2: For the lower surface and side of the accumulated dust, the discretized equations of the lower boundary and side thermal convection models are obtained according to formula (5) and formula (6) respectively; Where, T plate is the temperature of the carrier tube (5), N r is the radial grid index of the edge of the bearing tube (5); S24: Conduct a standard temperature hot plate experiment on accumulated dust and collect temperature data on the dust surface and the temperature data at several monitoring points inside the dust; S24-1: The inside of the carrying tube (5) is filled with the dust to be tested, and the thickness of the dust layer at each location in the carrying tube (5) is ensured to be uniform, so as to form accumulated dust to be tested; S24-2: Controlling the temperature controller to start working through the data processing terminal, so that the heating power supply supplies power to the heating resistance wire (6), and at the same time, controlling the heating temperature of the heating resistance wire (6) through the temperature controller, so that the temperature of the heat transfer plate (2) is constant within a preset temperature range; A first temperature signal in the dust layer is collected in real time by using a plurality of first thermocouples (3) located in the middle of the carrying tube (5) and sent to a data processing terminal; a second temperature signal on the surface of the heat transfer plate (2) is collected in real time by using a plurality of second thermocouples (4) located at the bottom of the carrying tube (5) and sent to the data processing terminal; an ambient temperature signal is collected in real time by using a temperature measuring device (8) and sent to the data processing terminal; the data processing terminal obtains first temperature data, second temperature data and ambient temperature data according to the first temperature signal and the second temperature signal respectively; At the same time, a thermal image acquisition device (7) is used to detect infrared radiation of accumulated dust in real time and generate a temperature image, which is then sent to a data processing terminal. The data processing terminal obtains upper surface temperature data of the dust based on the temperature image. S24-3: The data processing terminal divides the obtained plurality of first temperature data and the obtained plurality of second temperature data according to the position information of the plurality of first thermocouples (3) and the position information of the plurality of second thermocouples (4), and obtains the internal temperature data, the side temperature data and the lower surface temperature data of the accumulated dust respectively; S25: Performing theoretical numerical calculation of temperature conduction; inputting the obtained internal temperature data into the discretization equation of the heat conduction model, inputting the obtained upper surface temperature data, side surface temperature data and lower surface temperature data into the discretization equation of the heat convection model as boundary conditions, and determining the thermal conductivity k, convection heat transfer coefficient h and thermal diffusion coefficient α of the dust to be tested by calculation, and then obtaining the discretization equation of the heat conduction model and the discretization equation of the heat convection model for the dust to be tested; Step 3: Calculate the internal temperature of any accumulated dust and determine the location of the internal heat source; S31: bury multiple temperature sensors at key points inside any accumulated dust; S32: Scanning any accumulated dust with a laser scanner to obtain three-dimensional surface data of the accumulated dust, and sending the three-dimensional surface data to a data processing terminal; the data processing terminal generates a three-dimensional geometric model of the accumulated dust based on the three-dimensional surface data, and discretizes the three-dimensional form of the accumulated dust into a finite element network or a finite difference network to obtain a three-dimensional grid of the accumulated dust, and determines the coordinates (i, j, k) of each point; S33: using an infrared thermal imager to photograph the temperature distribution of any dust accumulation surface, and sending the temperature data of any dust accumulation surface to a data processing terminal; using a temperature sensor to collect key point temperature signals in real time, and sending them to the data processing terminal, and the data processing terminal obtains key point temperature data according to the key point temperature signals; S34: According to the temperature data of any dust accumulation surface, the temperature of the grid points on the outer surface of the three-dimensional grid is fixed to a known value T boundary ; S35: bringing the key point temperature data into the discretized equation of the general heat conduction model to establish the Laplace equation, as shown in formula (7); S36: Solve formula (7) to obtain the temperature at various locations inside any accumulated dust, and calculate the position of the heat source inside any accumulated dust by reverse fitting, and establish a three-dimensional temperature field of the accumulated dust based on the temperature data at various locations inside and the internal heat source position information, and then output the temperature data at various locations inside, the internal heat source position information and the three-dimensional temperature field to the visualization terminal, and display the temperature data at various locations inside, the internal heat position information and the three-dimensional temperature field in real time through the visualization terminal.

6. A method for measuring the internal temperature of accumulated dust and the location of heat sources according to claim 5, characterized in that: In step 1 S12, the discretized network is a hexahedron or a tetrahedron.

7. A method for measuring the internal temperature of accumulated dust and the location of heat sources according to claim 6, characterized in that: In step 3 S36, a thermodynamic iteration method or an efficient algorithm is used to calculate the temperature of any internal point.

8. A method for measuring the internal temperature of accumulated dust and the location of heat sources according to claim 7, characterized in that: In step three S36, the visualization terminal performs real-time display in the form of a thermal image or a three-dimensional temperature cloud map.

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