A real-time online monitoring system for plate-type heat exchanger leakage

Abstract

The present invention discloses a plate-type heat exchanger leakage real-time online monitoring system, which is composed of a leakage monitoring module, a central processing module and a human-computer interaction module. The leakage monitoring module includes a thermistor network and a current detection device. The thermistor network is arranged in a frame, the thermistor network is parallel to the plate, the thermistor network is connected to the current detection device, and the thermistor network is formed by a plurality of thermistor wires arranged horizontally and vertically in an interlaced manner. The central processing module includes a processor and a memory, and the human-computer interaction module includes an alarm and a touch screen. The plate-type heat exchanger leakage real-time online monitoring system disclosed in the present application can monitor the current value and resistance value of the thermistor wire in contact with the flue gas in real time through the thermistor network, realize the online monitoring function, accurate positioning, good effectiveness, and will not affect the circulation of the flue gas, and has low manufacturing cost. At the same time, a leakage coordinate calibration method and a current value correction method are set to make the monitoring result more accurate.

Description

Technical Field

[0001] The invention relates to the field of heat exchangers, and in particular to a real-time online monitoring system for leakage of a plate-type heat exchanger. Background Art

[0002] Heat exchangers are devices that transfer part of the heat of hot fluid to cold fluid, also known as heat exchangers. Heat exchangers play an important role in chemical, petroleum, power, food and many other industrial production. In chemical production, heat exchangers can be used as heaters, coolers, condensers, evaporators and reboilers.

[0003] According to the shape and structure of the heat transfer surface of the heat exchanger, the heat exchanger can be divided into tubular heat exchangers, plate heat exchangers, and special forms of heat exchangers. Among them, the plate heat exchanger includes a heat exchange plate, which is composed of a number of plates arranged in parallel.

[0004] In the process of thermal power generation, power plants use the heat energy generated by the combustion of combustibles and convert it into electrical energy through power generation devices, that is, fuel chemical energy → steam thermal energy → mechanical energy → electrical energy. In the process of combustible combustion turning water into high-temperature, high-pressure steam, part of the chemical energy of the fuel is converted into steam thermal energy, and the other part of the chemical energy of the fuel is not absorbed by water and is converted into hot fluid.

[0005] If the hot fluid is discharged directly, not only will the temperature of the fluid be too high to meet the discharge standard, but also the energy loss generated in the process of converting the chemical energy of the fuel into steam thermal energy will be large. Therefore, the plate heat exchanger is used to transfer part of the heat of the hot fluid to the cold fluid, which can not only make the fluid temperature reach the specified index of the process, but also improve the energy utilization rate.

[0006] Since the power plant generates a lot of energy, the plate heat exchanger used is relatively large, so the plate installed in the heat exchanger is also relatively large. During use, the plate may be damaged, resulting in leakage. Since damage is a form of loss in use, the damaged part is often small, and the leakage point is also small. During maintenance, the staff needs to find the leakage point on the larger plate and then repair it in a targeted manner.

[0007] It usually takes a long time to find the leak point. The staff needs to apply a foaming layer on the surface of the plate and then inflate the plate. Several bubbles will be blown out at the leak point to remind the staff that there is damage there.

[0008] In order to improve the efficiency of finding leakage points, the existing invention patent disclosed in the application publication number CN108844688A uses a thermal resistor temperature measuring probe to monitor the temperature information at different positions of the heat exchange medium pipeline of the heat exchanger in real time. The advantage is that the leakage point can be quickly determined. The disadvantage is that the monitoring accuracy is related to the setting density of the thermal resistor temperature measuring probe. If the setting density of the thermal resistor temperature measuring probe is high, the monitoring accuracy is high and the monitoring cost is high. The thermal resistor temperature measuring probe has a certain size of volume, and the high-density setting will affect the flue gas circulation; if the setting density of the thermal resistor temperature measuring probe is low, the monitoring accuracy is low and the monitoring effect is poor. Summary of the invention

[0009] The purpose of the present invention is to construct a real-time online monitoring system for plate-type heat exchanger leakage based on the existing heat exchanger and the need for real-time online monitoring of whether there is leakage in the plate.

[0010] A real-time online monitoring system for leakage of a plate-type heat exchanger is applied in a heat exchanger, wherein the heat exchanger comprises a frame and a plate, wherein the plate is arranged in the frame, wherein the plates are arranged parallel to each other, and the intervals between two adjacent plates are uniform, wherein the arrangement direction of the plates is perpendicular to the flow direction of a hot fluid, wherein the plates are composed of two layers of metal plates welded at the edges, and wherein welding points are regularly arranged inside, wherein after inflation, the non-welding point part inside the plates bulges outward, wherein the bulge forms a flow channel between the two layers of metal plates, wherein a cold fluid is circulated in the flow channel, wherein the monitoring system comprises a leakage monitoring module, a central processing module, and a human-computer interaction module, wherein the leakage monitoring module performs leakage monitoring based on the characteristic that the resistance value of a metal conductor increases with the increase of temperature, wherein the leakage monitoring module comprises a thermistor network for performing leakage monitoring, and a current detection device for detecting the current size of each thermistor wire in the thermistor network, wherein the thermistor network is arranged in the frame, wherein the thermistor network is parallel to the plate, and wherein the thermistor network is connected to the current detection device;

[0011] The thermistor network is formed by a plurality of thermistor wires arranged in a staggered manner horizontally and vertically;

[0012] The central processing module includes a processor for collecting and processing the current value and resistance value signals monitored in real time on the thermistor network, and a memory for storing data processing programs and data;

[0013] The human-computer interaction module includes an alarm that can alert the staff of leakage in an audio-visual form, and a touch screen that can transmit instructions to the central processing module and view and retrieve monitoring data.

[0014] Furthermore, the size of the thermistor net corresponds to the size of the bulging part of the plate, so as to ensure that each position of the flow channel on the plate is monitored.

[0015] Furthermore, the thermistor network is connected to an independent power supply, and the thermistor network is wrapped with an insulating layer.

[0016] When the plate leaks, the smoke temperature around the leakage point will drop, and the resistance of the thermistor wire in the thermistor network that is in contact with the cooled smoke will change. The current detection device detects the current value of the thermistor wire and feeds it back to the processor. After processing and analysis, the leakage information is fed back to the touch screen, and the alarm is triggered to remind the staff that the plate has leaked.

[0017] Further, the thermistor wires staggered horizontally and vertically in the thermistor network are divided into horizontally distributed thermistor wires and vertically distributed thermistor wires, the spacing between the horizontally distributed thermistor wires is equal, the spacing between the vertically distributed thermistor wires is equal, and the spacing between two adjacent horizontally distributed thermistor wires is equal to the spacing between two adjacent vertically distributed thermistor wires;

[0018] The thermistor wires staggered horizontally and vertically will form a number of grids, and different horizontal thermistor wires and vertical thermistor wires intersect to form different grid points, where the thermistor wire positions at the grid points intersect, but the lines do not intersect.

[0019] Specifically, the thermistor wire adopts a positive temperature coefficient, and all the thermistor wires are connected in parallel in the circuit;

[0020] Each of the thermistor wires is connected to an independent current detection device.

[0021] In order to accurately locate the leak, the following method is proposed:

[0022] The flow direction of the thermal fluid is taken as the standard, the flow direction is from front to back, and the vertical plane of the thermistor network is used as the reference plane to build a coordinate system, the horizontal direction is the X axis, the vertical direction is the Y axis, the intersection of the X axis and the Y axis is the zero point O (0, 0), the positive direction of the X axis is from front to back, and the positive direction of the Y axis is from bottom to top.

[0023] Assume that each small grid of the grid is a small unit with a unit of 1, and the spacing between two adjacent thermistor wires is a unit of 1, then the coordinates of the horizontally distributed thermistor wires on the Y axis are y=0, 1, 2, 3, ..., y∈N from bottom to top, N is a natural number, y=α-1, α is the order of the horizontal thermistor wires arranged from bottom to top;

[0024] The coordinates of the vertically distributed thermistor wires on the X-axis are x=0, 1, 2, 3, ..., x∈N from front to back, N is a natural number, x=β-1, β is the order of the vertical thermistor wires arranged from front to back;

[0025] Zero point O is the intersection of the first thermistor wire from top to bottom and the first thermistor wire from front to back;

[0026] Assume that the standard current value set by the current detection device is i, the variable current is h, and the actual current value i measured by the current detection device is ’ ,i ’ ∈[ih,i+h];

[0027] If the resistance value of the vertically distributed thermistor wire is different from the resistance value of the horizontally distributed thermistor wire, the standard current value i and the variable current value set by the current detection device connecting the vertically distributed thermistor wire and the horizontally distributed thermistor wire are also different.

[0028] When the plate leaks, the cold fluid inside the plate flows out, the smoke temperature at the leaking point decreases, and the resistance of the thermistor wire in contact with the smoke with reduced temperature increases. The corresponding current detection device detects a decrease in current on the thermistor wire. When the actual current value measured by the current detection device exceeds the variation range, the current value of the thermistor wire is fed back to the processor and marked. The leakage coordinates P (β-1, α-1) are then obtained based on the feedback information, and the staff can locate the leakage point of the plate based on the leakage coordinates.

[0029] Since there is a gap between the plate and the thermistor network, and the smoke is in a flowing state, there is a deviation between the monitored leakage coordinate P and the actual leakage point. Therefore, in order to improve the positioning accuracy of the monitored leakage point, a leakage coordinate calibration method is proposed.

[0030] Furthermore, the leakage coordinate calibration method is as follows:

[0031] (1) Select any point in the coordinate system as the preset leakage coordinate Q, and artificially drill a leakage point on the plate corresponding to the position of the preset leakage coordinate Q (x, y);

[0032] (2) Install the excavated plate into the heat exchanger and simulate the actual working conditions of the heat exchanger to measure the test leakage coordinates. Repeat the simulation to measure n groups of test leakage coordinates: P1 (x1, y1), P2 (x2, y2), P3 (x3, y3), ..., P n (x n ,y n );

[0033] (3) Take the calibration deviation between each test leakage coordinate and the preset leakage coordinate,

[0034] First take the arithmetic mean deviation of point x on the X-axis, , i≤n, i∈N, N is a natural number,

[0035] Then take the arithmetic mean deviation of point y on the Y axis, , i≤n, i∈N, N is a natural number,

[0036] So the calibration deviation is ;

[0037] (4) Finally, the corrected leakage coordinates P are obtained ’ (beta-1-a, alpha-1-b).

[0038] Under actual working conditions, there is a certain temperature difference in the flue gas distributed in the heat exchanger, and the temperature variation rule is: the flue gas temperature gradually decreases from front to back, and the flue gas temperature gradually decreases from top to bottom. The resistance value of the thermistor wire in contact with flue gas of different temperatures is different, and the current value detected by the current detection device connected to the thermistor wire is also different. Therefore, it is necessary to propose a current value correction method to correct the deviation of the current value measured by the current detection device caused by uneven flue gas temperature.

[0039] During leakage monitoring, the current value measured by the current detection device must first be corrected for deviation before determining whether it exceeds the current change amount.

[0040] The current value correction method is as follows:

[0041] (1) Simulating the actual working conditions of the heat exchanger, the current values ​​on the vertically distributed thermistor wires from front to back during normal operation are as follows: i x(0) 、i x(1) 、i x(2) ,…,i x(max) ; The current values ​​on the horizontally distributed thermistor wires from bottom to top are: i y(0) 、i y(1) 、i y(2) ,…,i y(max) ;

[0042] (2) Take the coordinates of the intersection of the last thermistor wire from bottom to top in the horizontal distribution and the first thermistor wire from front to back in the vertical distribution (0, y max ), y max =α-1, α takes the maximum value, record the coordinates (0, y max ) is the standard coordinate, and the current value of the vertically distributed thermistor wire that constitutes the standard coordinate is i x(0), the current value of the horizontally distributed thermistor wire is i y(max) , record the current value i x(0) is the standard current of the X-axis, and the current value i y(max) is the standard current of Y axis;

[0043] (3) Take the current value i on the remaining vertically distributed thermistor wires x(1) 、i x(2) ,…,i x(max) With the current value i x(0) The absolute value of the difference, the absolute value δi x(1) =|i x(1) -i x(0) |,δi x(2) =|i x(2) -i x(0) |,…,δi x(max) =|i x(max) -i x(0) |; Take the current value i on the other horizontally distributed thermistor wires y(0) 、i y(1) ,…,i y(max-1) With the current value i y(max) The absolute value of the difference, the absolute value δi y(0) =|i y(0) -i y(max) |,δi y(1) =|i y(1) -i y(max) |,…,δi y(max-1) =|i y(max-1) -i y(max) |;

[0044] (4) Current value i x(1) Correction to i x(1) '=i x(1) -δi x(1) , current value i x(2) Correction to i x(2) '=i x(2) -δi x(2) ,…,current value i x(max) Correction to i x(max) '=i x(max) -δi x(max) ;

[0045] By analogy, the current value i x(k) Correction to i x(k) ’ =i x(k) -δi x(k) , k is a natural number;

[0046] Current value i y(0)Correction to i y(0) ’ =i y(0) -δi y(0) , current value i y(1) Correction to i y(1) ’ =i y(1) -δi y(1) ,…,current value i y(max-1) Correction to i y(max-1) ’ =i y(max-1) -δi y(max-1) ;

[0047] By analogy, the current value i y(f) Correction to i y(f) ’ =i y(f) -δi y(f) , f is a natural number.

[0048] Furthermore, the heat exchanger adopts a single-piece detachable structure, the plate is detachably installed in the frame, the connection parts are on the front and back sides of the frame, and the thermistor network is installed on the plate and located on one side of the plate.

[0049] The beneficial effects of the present invention are as follows: a real-time online monitoring system for plate-type heat exchanger leakage disclosed in the present application can monitor the current value and resistance value of the thermistor wire in contact with the flue gas in real time through a thermistor network, and combined with the characteristic that the resistance value of a metal conductor increases with the increase of temperature, the real-time online monitoring function of the plate-type heat exchanger is realized, and a coordinate system is established through the thermistor wires that cross horizontally and vertically, and the leakage position of the plate is locked through the intersecting coordinate points, with accurate positioning and good effectiveness, and the thermistor wire is small in size, even if a high-density monitoring network coordinate is set, it will not affect the circulation of the flue gas, and the manufacturing cost is low, and a leakage coordinate calibration method and a current value correction method are set at the same time, which solves the problem of the offset of the monitored leakage coordinates caused by the circulation of the flue gas, and solves the problem of the deviation of the current value on the thermistor wire caused by the uneven distribution of the flue gas, so that the monitoring result is more accurate.

[0050] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following specifically cites a preferred embodiment and describes it in detail with the accompanying drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0052] Figure 1 It is a schematic diagram of the overall structure of a specific example of the application of the monitoring system of the present invention;

[0053] Figure 2 yes Figure 1 Schematic diagram of the structure at AA in the middle;

[0054] Figure 3 yes Figure 1 Schematic diagram of the structure at the middle BB;

[0055] Figure 4 This is a schematic diagram of the structure of the A-type plate monitored by the monitoring system of the present invention.

[0056] Figure 5 It is a schematic diagram of the structure of the B-type plate monitored by the monitoring system of the present invention;

[0057] Figure 6 It is a structural schematic diagram of a specific example of the monitoring system of the present invention;

[0058] Figure 7 is a schematic diagram of a leakage monitoring module in a specific example of the monitoring system of the present invention;

[0059] Figure 8 is a schematic diagram of a coordinate system established in a specific example of the monitoring system of the present invention;

[0060] In the figure: 101, frame; 102, plate; 103, top hanging piece; 104, outer frame; 107, inner net; 108, type A plate; 109, type B plate; 110, thermistor net; 112, current detection device; 113, vertical thermistor wire; 121, horizontal thermistor wire; 122, power supply. DETAILED DESCRIPTION

[0061] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0062] A real-time online monitoring system for leakage of a plate-type heat exchanger of the present invention is further described in conjunction with the accompanying drawings.

[0063] like Figure 1 and Figure 2 As shown, the monitoring system described in this embodiment is arranged in a heat exchanger, and the heat exchanger includes a frame 101 and a plate 102. The heat exchanger adopts a single-piece detachable structure, and the plate 102 is detachably installed in the frame 101, and the connection parts are on the front and back sides of the frame 101.

[0064] The plates 102 are arranged parallel to each other and the intervals between two adjacent plates 102 are uniform. The arrangement direction of the plates 102 is perpendicular to the flow direction of the thermal fluid. Each plate 102 is provided with a thermistor net 110, which is welded to the right side of the plate 102 through a connecting piece. The thermistor net 110 and the plate 102 are parallel to each other.

[0065] like Figure 3 , Figure 4 and Figure 5 As shown, the plate 102 is composed of two layers of metal plates welded at the edges, and weld points are regularly arranged inside. After inflation, the non-welded part of the plate 102 bulges outward, forming a flow channel between the two layers of metal plates, and a cold fluid is circulated in the flow channel.

[0066] The welding points on the plate 102 for connecting the thermistor mesh 110 are located at the edges of the plate 102 .

[0067] The size of the thermistor mesh 110 corresponds to the size of the bulging portion of the plate 102 .

[0068] A top hanger 103 is provided above the plate 102 . The length of the top hanger 103 is greater than the distance between the front and rear inner walls of the frame 101 , and the length of the top hanger 103 is less than or equal to the distance between the front and rear outer walls of the frame 101 . The top hangers 103 are all arranged on the right side of the upper edge of the plate 102 .

[0069] The plate 102 includes an A-type plate 108 and a B-type plate 109, which are alternately arranged and fixedly connected to the frame 101 by bolts arranged at the front and rear edges thereof. This can make the arrangement of the plates more compact and improve the performance of the heat exchanger.

[0070] like Figure 6 and Figure 7 As shown, the thermistor mesh 110 includes an outer frame 104 and an inner mesh 107 , the inner mesh 107 is fixed on the outer frame 104 , and welding points on the thermistor mesh 110 for connecting the plate 102 are located on the outer frame 104 .

[0071] The outer frame 104 defines a hollow cavity therein.

[0072] An insulating layer is disposed on the outer periphery of the thermistor network 110 , and the thermistor network 110 is connected to a power source 122 .

[0073] The inner network 107 includes 10×43 thermistor wires that are staggered horizontally and vertically. The thermistor wires are all connected in parallel in the circuit, and each thermistor wire is connected to an independent current detection device 112. The thermistor wires are divided into vertical thermistor wires 113 and horizontal thermistor wires 121. 10×43 means that there are 10 vertical thermistor wires 113 and 43 horizontal thermistor wires 121. The vertical thermistor wires 113 and the horizontal thermistor wires 121 form a grid. The small grids in the grid are squares, and the sizes of the small grids are the same. Different vertical thermistor wires 113 and horizontal thermistor wires 121 will intersect to form different network points. The vertical thermistor wires 113 and the horizontal thermistor wires 121 at the network points intersect, and the circuits do not intersect.

[0074] Any two vertical thermistor wires 113 are parallel to each other, and the distances between any two adjacent vertical thermistor wires 113 are the same.

[0075] Any two horizontal thermistor wires 121 are parallel to each other, and the intervals between any two adjacent horizontal thermistor wires 121 are the same.

[0076] The vertical thermistor wire 113 and the horizontal thermistor wire 121 are both thermistor wires with positive temperature coefficients.

[0077] The current detection device 112 is disposed in the hollow cavity inside the outer frame 104 .

[0078] The monitoring system is composed of a leakage monitoring module, a central processing module and a human-computer interaction module. The thermistor network 110 and the current detection device 112 constitute the leakage monitoring module. The human-computer interaction module includes an alarm and a touch screen. The operator can send instructions to the central processing module through the touch screen. The alarm can receive signals from the central processing module and issue an alarm. The central processing module includes a processor and a memory. The processor can send and receive instructions and process received data signals. The memory can store data processing programs and data.

[0079] When the plate 102 leaks, the smoke temperature around the leak point will drop, and the resistance of the thermistor wire in contact with the cooled smoke will decrease. The current value of the thermistor wire detected by the current detection device 112 will increase and be fed back to the processor. After processing and analysis, the leakage information will be fed back to the touch screen, and the alarm will be triggered to remind the staff that the plate has leaked.

[0080] The specific steps for leak monitoring and locating are as follows:

[0081] (1) If Figure 8As shown, a coordinate system is established with the vertical plane of the thermistor network 110 as a reference plane, the horizontal direction is the X-axis, the vertical direction is the Y-axis, the intersection of the X-axis and the Y-axis is the zero point O (0, 0), the positive direction of the X-axis is from front to back, the positive direction of the Y-axis is from bottom to top, and the zero point O is the intersection of the first horizontal thermistor wire 121 from top to bottom and the first vertical thermistor wire 113 from front to back;

[0082] (2) Assuming that each small grid in the grid is a small unit with a unit of 1, and the spacing between two adjacent thermistor wires is a unit of 1, then the coordinates of the horizontal thermistor wires 121 on the Y axis are y=0, 1, 2, 3, ..., 41, 42 from bottom to top, and y=α-1, α is the order of the horizontal thermistor wires 121 arranged from bottom to top;

[0083] The coordinates of the vertical thermistor wires 113 on the X-axis are x=0, 1, 2, 3, ..., 8, 9 from front to back, and x=β-1, β is the order of the vertical thermistor wires 113 arranged from front to back;

[0084] (3) The above-mentioned thermistor wire is made of a metal material with a temperature range of 0-300°C and a resistivity p of 0.20-0.74μΩ·m. The resistivity changes linearly with temperature. The resistivity satisfies p=0.2+0.0018T (μΩ·m) in the temperature range of 0-300°C, where T is the temperature. The length l1 of the horizontal thermistor wire 121 is 2m, the length l2 of the vertical thermistor wire 113 is 8.6m, and the diameter of the cross section of the thermistor wire is 0.4mm.

[0085] According to the resistance calculation formula R=pl / s and the circular cross-section calculation formula s=πr 2 It can be seen that

[0086] The cross-sectional area of ​​the horizontal thermistor wire 121 is s1=0.1256×10 -6 m 2 ,

[0087] The resistance value of the horizontal thermistor wire 121 is R1=[(0.2+0.0018T)×10 -6 ×2] / [0.1256×10 -6 ]Ω,

[0088] The resistance value of the vertical thermistor wire 113 is R2=[(0.2+0.0018T)×10 -6 ×8.6] / [0.1256×10 -6 ]Ω,

[0089] The voltage U of the power supply 122 is 5V.

[0090] The flue gas temperatures at any five coordinates in the heat exchanger are measured, which are 277.3°C, 267.2°C, 276.2°C, 272.8°C, and 263.5°C, respectively. The average value of the measured flue gas temperatures is taken as T 平 is 271.4℃,

[0091] Then R1=10.96Ω, R2=47.14Ω,

[0092] The current detection device 112 measures the current values ​​of the thermistor wire 121 at any five coordinate levels, which are 269.5mA, 274.6mA, 271.7mA, 270.3mA, and 275.2mA respectively, and takes the average value of the measured current i 平 is 274.3mA,

[0093] The changing current value h1 on the horizontal thermistor wire 121 is 20mA.

[0094] The current value of the horizontal thermistor wire 121 measured by the current detection device 112 is within the range of [274.3-20, 274.3+20]. The current deviation is a normal fluctuation and will not mark a leakage.

[0095] The current detection device 112 measures the current values ​​of the thermistor wire 113 at any five coordinates, which are 62.7mA, 63.1mA, 62.4mA, 62.3mA, and 63.3mA respectively, and takes the average value of the measured current i 平 is 62.8mA,

[0096] The changing current value h2 on the vertical thermistor wire 113 is 5 mA.

[0097] The current value of the vertical thermistor wire 113 measured by the current detection device 112 is within the range of [62.8-5, 62.8+5]. The current deviation is a normal fluctuation and will not mark a leakage.

[0098] (4) The current value on the horizontal thermistor wire 121 constituting the coordinate (3, 37) is measured to be 296.4 mA, and the current value on the vertical thermistor wire 113 constituting the coordinate (3, 37) is 69.3 mA. The current values ​​on the horizontal thermistor wire 121 and the vertical thermistor wire 113 are both beyond the set variation range, indicating a leakage at P (3, 37).

[0099] The current values ​​measured by the current detection device 112 are all calibrated current values.

[0100] Since there is a gap between the plate 102 and the thermistor net 110 and the smoke is in a flowing state, there is a deviation between the monitored leakage coordinates (3, 37) and the actual leakage point. The actual operation of the proposed leakage coordinate calibration method is as follows:

[0101] (1) Select (4, 20) as the preset leakage coordinate in the coordinate system, and manually drill a leakage point on the plate 102, the position of which corresponds to (4, 20);

[0102] (2) The excavated plates were installed in the heat exchanger, and the actual working conditions of the heat exchanger were simulated. Ten groups of test leakage coordinates were measured: P1 (5, 18), P2 (6, 18), P3 (5, 19), P4 (5, 20), P5 (5, 20), P6 (6, 19), P7 (6, 17), P8 (5, 20), P9 (7, 19), P 10 (5, 18);

[0103] (3) Take the calibration deviation between each test leakage coordinate and the preset leakage coordinate,

[0104] First take the arithmetic mean deviation of point x on the X-axis, , i≤n, i∈N, N is a natural number, a=1.5,

[0105] Then take the arithmetic mean deviation of point y on the Y axis, , i≤n, i∈N, N is a natural number, b=1.2,

[0106] The calibration deviation is obtained as ;

[0107] (4) Calibrate the leakage coordinates P (3, 37) and after correction, the leakage coordinates P ’ (1.5, 35.8).

[0108] In actual working conditions, there is a certain temperature difference in the flue gas distributed in the heat exchanger, and the temperature variation rule is: the flue gas temperature gradually decreases from front to back, and the flue gas temperature gradually decreases from top to bottom. The resistance values ​​of thermistor wires in contact with flue gas of different temperatures are different, and the current values ​​detected by different thermistor wires are also different, so it is necessary to propose a current value correction method to correct the deviation of the current value measured by the current detection device 112 caused by uneven flue gas temperature.

[0109] During leakage monitoring, the current value measured by the current detection device must first be corrected for current value deviation before determining whether it exceeds the current change amount.

[0110] The current value correction method is as follows:

[0111] Step 1: simulate the actual working condition of the heat exchanger, and measure the current values ​​on the vertical thermistor wire 113 from front to back during normal operation: i x(0) =63.9mA, i x(1) =65.1mA, i x(2)= 66.1mA, i x(3) = 67.2mA, i x(4) = 68.4mA, i x(5) = 69.5mA, i x(6) = 70.7mA, i x(7) = 72.0mA, i x(8) = 73.3mA, i x(9) = 74.6mA;

[0112] Horizontal heating electric current barrier 121 upper electric current flow lower supreme separation: i y(0) = 279.3mA, i y(1) =279.0mA, i y(2) =278.5mA, i y(3) =278.2mA, i y(4) =277.9mA, i y(5) =277.4mA, i y(6) = 277.1mA, i y(7) =276.8mA, i y(8) =276.3mA, i y(9) =276.0mA, i y(10) =275.7mA, i y(11) = 275.4mA, i y(12) =274.9mA, i y(13) =274.6mA, i y(14) = 274.4mA, i y(15) =273.8mA, i y(16) = 273.6mA, i y(17) = 273.3mA, i y(18) =272.8mA, i y(19) =272.5mA, i y(20) =272.2mA, i y(21) =271.7mA, i y(22) =271.4mA, i y(23) =271.2mA, i y(24) =270.6mA, i y(25) =270.4mA, i y(26) =270.1mA, i y(27) = 269.6mA, i y(28) = 269.3mA, i y(29) =269.0mA, i y(30) =268.8mA, i y(31) =268.3mA, i y(32) =267.8mA, i y(33) =267.8mA, iy(34) =267.3mA, i y(35) =267.0mA, i y(36) =266.8mA, i y(37) =266.2mA, i y(38) =266.0mA, i y(39) =265.7mA, i y(40) =265.2mA, i y(41) =265.0mA, i y(42) =264.7mA;

[0113] Step 2: Take the coordinate (0,42) as the standard coordinate. The current value of the vertical thermistor wire 113 constituting the standard coordinate is i x(0) =63.9mA, the current value of the horizontal thermistor wire 121 constituting the standard coordinate is i y(42) =264.7mA, record the current value i x(0) is the standard current of the X-axis, and the current value i y(42) is the standard current of Y axis;

[0114] Step 3: Take the current value i on the remaining vertical thermistor wires 113 x(1) 、i x(2) ,…,i x(9) With the current value i x(0) The absolute value of the difference, the absolute value δi x(1) =|i x(1) -i x(0) |=1.2mA,

[0115] δi x(2) =|i x(2) -i x(0) | =2.2mA,

[0116] δi x(3) =|i x(3) -i x(0) | =3.3mA,

[0117] δi x(4) =|i x(4) -i x(0) | =4.5mA,

[0118] δi x(5) =|i x(5) -i x(0) | =5.6mA,

[0119] δi x(6) =|i x(6) -i x(0) | =6.8mA,

[0120] δi x(7) =|i x(7) -i x(0) | =8.1mA,

[0121] δi x(8) =|i x(8) -i x(0) | =9.4mA,

[0122] δi x(9) =|i x(9) -i x(0) | =10.7mA;

[0123] Take the current value i on the remaining horizontal thermistor wire 121 y(0) 、i y(1) ,…,i y(41) With the current value i y(42) The absolute value of the difference, the absolute value δi y(0) =|i y(0) -i y(42) |=14.6mA,

[0124] δi y(1) =|i y(1) -i y(42) |=14.3mA,

[0125] δi y(2) =|i y(2) -i y(42) |=13.8 mA,

[0126] δi y(3) =|i y(3) -i y(42) |=13.5mA,

[0127] δi y(4) =|i y(4) -i y(42) |=13.2mA,

[0128] δi y(5) =|i y(5) -i y(42) |=12.7mA,

[0129] δi y(6) =|i y(6) -i y(42) |=12.4mA,

[0130] δi y(7) =|i y(7) -i y(42) |=12.1mA,

[0131] δi y(8) =| i y(8) - i y(42) |=11.6mA,

[0132] δi y(9) =| i y(9) - i y(42) |=11.3mA,

[0133] δi y(10) =| i y(10) - i y(42) |=11.0mA,

[0134] δi y(11) =| i y(11) - i y(42) |=10.7mA,

[0135] δi y(12) =| i y(12) - i y(42) |=10.2mA,

[0136] δi y(13) =| i y(13) - i y(42) |=9.9mA,

[0137] δi y(14) =| i y(14) - i y(42) |=9.7mA,

[0138] δi y(15) =| i y(15) - i y(42) |=9.1mA,

[0139] δi y(16) =| i y(16) - i y(42) |=8.9mA,

[0140] δi y(17) =| i y(17) - i y(42) |=8.6mA,

[0141] δi y(18) =| i y(18) - i y(42) |=8.1mA,

[0142] δi y(19) =| i y(19) - i y(42) |=7.8mA,

[0143] δi y(20) =| i y(20) - i y(42) |=7.5mA,

[0144] δi y(21) =| i y(21) - i y(42) |=7.0mA,

[0145] δi y(22) =| i y(22) - i y(42) |=6.7mA,

[0146] δi y(23) =| i y(23) - i y(42) |=6.5mA,

[0147] δi y(24) =| i y(24) - i y(42) |=6.1mA,

[0148] δi y(25) =| i y(25) - i y(42) |=5.9mA,

[0149] δi y(26) =| i y(26) - i y(42) |=5.6mA,

[0150] δi y(27) =| i y(27) - i y(42) |=4.9mA,

[0151] δi y(28) =| i y(28) - i y(42) |=4.6mA,

[0152] δi y(29) =| i y(29) - i y(42) |=4.3mA,

[0153] δi y(30) =| i y(30) - i y(42) |=4.1mA,

[0154] δi y(31) =| i y(31) - i y(42) |=3.6mA,

[0155] δiy(32) =| i y(32) -i y(42) |=3.1mA,

[0156] δi y(33) =| i y(33) -i y(42) |=3.1mA,

[0157] δi y(34) =| i y(34) -i y(42) |=2.6mA,

[0158] δi y(35) =| i y(35) -i y(42) |=2.3mA,

[0159] δi y(36) =| i y(36) -i y(42) |=2.1mA,

[0160] δi y(37) =| i y(37) -i y(42) |=1.5mA,

[0161] δi y(38) =| i y(38) -i y(42) |=1.3mA,

[0162] δi y(39) =| i y(39) -i y(42) |=1.0mA,

[0163] δi y(40) =| i y(40) -i y(42) |=0.5mA,

[0164] δi y(41) =| i y(41) -i y(42) |=0.3mA,

[0165] Step 4, electric current i x(k) Proofreading x(k) ’ =i x(k) - δi x(k) ,k∈[1,9], k natural number, electric current i y(f) Proofreading y(f) ’ =i y(f) - δi y(f),f∈[0,41], f is a natural number.

[0166] What is described above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A real-time online monitoring system for plate-type heat exchanger leakage, applied in a heat exchanger, wherein the heat exchanger comprises a frame and plates, wherein the plates are arranged in the frame, wherein the plates are arranged parallel to each other, and the intervals between two adjacent plates are uniform, wherein the arrangement direction of the plates is perpendicular to the flow direction of the hot fluid, wherein the plates are composed of two layers of metal plates welded at the edges, and wherein welding points are regularly arranged inside, and after being inflated, the non-welding point part inside the plates bulges outward, wherein the bulge forms a flow channel between the two layers of metal plates, wherein a cold fluid is circulated in the flow channel, wherein the cold fluid is arranged in the flow channel, wherein the cold fluid is circulated ... The monitoring system is composed of a leakage monitoring module, a central processing module and a human-computer interaction module. The leakage monitoring module performs leakage monitoring based on the characteristic that the resistance value of a metal conductor increases with the increase of temperature. The leakage monitoring module includes a thermistor network for leakage monitoring and a current detection device for detecting the current size of each thermistor wire in the thermistor network. The thermistor network is arranged in the frame, the thermistor network and the plate are parallel to each other, and the thermistor network is connected to the current detection device. The thermistor network is formed by a plurality of thermistor wires arranged in a staggered manner horizontally and vertically; The central processing module includes a processor for collecting and processing the current value and resistance value signals monitored in real time on the thermistor network, and a memory for storing data processing programs and data; The human-computer interaction module includes an alarm that can alert the staff of leakage in an audio-visual form, and a touch screen that can transmit instructions to the central processing module and view and retrieve monitoring data; The thermistor wires staggered horizontally and vertically will form a number of grids, and different horizontal thermistor wires and vertical thermistor wires intersect to form different grid points, the thermistor wire positions at the grid points intersect, and the lines do not intersect; The thermistor wire has a positive temperature coefficient, and all the thermistor wires are connected in parallel in the circuit; Each of the thermistor wires is connected to an independent current detection device; A real-time online monitoring system for plate-type heat exchanger leakage accurately locates the leakage through the following methods: The flow direction of the thermal fluid is taken as the standard, the flow direction is from front to back, and the vertical plane of the thermistor network is used as the reference plane to build a coordinate system, the horizontal direction is the X axis, the vertical direction is the Y axis, the intersection of the X axis and the Y axis is the zero point O (0, 0), the positive direction of the X axis is from front to back, and the positive direction of the Y axis is from bottom to top. Assume that each small grid of the grid is a small unit with a unit of 1, and the spacing between two adjacent thermistor wires is a unit of 1, then the coordinates of the horizontally distributed thermistor wires on the Y axis are y=0, 1, 2, 3, ..., y∈N from bottom to top, N is a natural number, y=α-1, α is the order of the horizontal thermistor wires arranged from bottom to top; The coordinates of the vertically distributed thermistor wires on the X-axis are x=0, 1, 2, 3, ..., x∈N from front to back, N is a natural number, x=β-1, β is the order of the vertical thermistor wires arranged from front to back; Zero point O is the intersection of the first thermistor wire from top to bottom and the first thermistor wire from front to back; Assume that the standard current value set by the current detection device is i, the variable current is h, and the actual current value i measured by the current detection device is ’ ,i ’ ∈[ih,i+h]; When the plate leaks, the cold fluid inside the plate flows out, the smoke temperature at the leaking point decreases, the resistance of the thermistor wire in contact with the smoke with reduced temperature increases, and the corresponding current detection device detects that the current on the thermistor wire decreases. When the actual current value measured by the current detection device exceeds the variation range, the current value of the thermistor wire marked with abnormality is fed back to the processor and marked, and then the leakage coordinates P (β-1, α-1) are obtained according to the feedback information, and the staff can locate the leakage point of the plate according to the leakage coordinates; A real-time online monitoring system for plate-type heat exchanger leakage is calibrated by the following method: (1) Select any point in the coordinate system as a preset leakage coordinate Q, and manually drill a leakage point on the plate corresponding to the preset leakage coordinate Q (x, y); (2) Install the excavated plate into the heat exchanger and simulate the actual working conditions of the heat exchanger to measure the test leakage coordinates. Repeat the simulation to measure n groups of test leakage coordinates: P1 (x1, y1), P2 (x2, y2), P3 (x3, y3), ..., P n (x n ,y n ); (3) Take the calibration deviation between each test leakage coordinate and the preset leakage coordinate, First take the arithmetic mean deviation of point x on the X-axis, , i≤n, i∈N, N is a natural number, Then take the arithmetic mean deviation of point y on the Y axis, , i≤n, i∈N, N is a natural number, So the calibration deviation is ; (4) Finally, the corrected leakage coordinate P is obtained ’ (beta-1-a, alpha-1-b); A real-time online monitoring system for plate heat exchanger leakage performs current value correction by the following method: (1) Simulating the actual working conditions of the heat exchanger, the current values ​​on the vertically distributed thermistor wires from front to back during normal operation are as follows: i x(0) 、i x(1) 、i x(2) ,…,i x(max) ; The current values ​​on the horizontally distributed thermistor wires from bottom to top are: i y(0) 、i y(1) 、i y(2) ,…,i y(max) ; (2) Take the coordinates of the intersection of the last thermistor wire from bottom to top in the horizontal distribution and the first thermistor wire from front to back in the vertical distribution (0, y max ), y max =α-1, α takes the maximum value, record the coordinates (0, y max ) is the standard coordinate, and the current value of the vertically distributed thermistor wire that constitutes the standard coordinate is i x(0) , the current value of the horizontally distributed thermistor wire is i y(max) , record the current value i x(0) is the standard current of the X axis, the current value i y(max) is the standard current of Y axis; (3) Take the current value i on the remaining vertically distributed thermistor wires x(1) 、i x(2) ,…,i x(max) With the current value i x(0) The absolute value of the difference, the absolute value δi x(1) =|i x(1) -i x(0) |,δi x(2) =|i x(2) -i x(0) |,…,δi x(max) =|i x(max) -i x(0) |; Take the current value i on the other horizontally distributed thermistor wires y(0) 、i y(1) ,…,i y(max-1) With the current value i y(max) The absolute value of the difference, the absolute value δi y(0) =|i y(0) -i y(max) |,δi y(1) =|i y(1) -i y(max) |,…,δi y(max-1) =|i y(max-1) -i y(max) |; (4) Correction current value i x(1) for i x(1) '=i x(1) -δi x(1) , correction current value i x(2) for i x(2) '=i x(2) -δi x(2) ,…,current value i x(2) for i x(max) '=i x(max) -δi x(max) ; By analogy, x(k) for i x(k) ’ =i x(k) -δi x(k) , k is a natural number; Correction current value i y(0) for i y(0) '=i y(0) -δi y(0) , correction current value i y(1) for i y(1) '=i y(1) -δi y(1) ,…,current value i y(max-1) for i y(max-1) '=i y(max-1) -δi y(max-1) ; By analogy, y(f) for i y(f) '=i y(f) -δi y(f) , f is a natural number.

2. The monitoring system according to claim 1, characterized in that: The size of the thermistor net corresponds to the size of the bulging portion of the plate.

3. The monitoring system according to claim 1, characterized in that: The thermistor network is connected to an independent power supply, and an insulating layer is wrapped outside the thermistor network.

4. The monitoring system according to claim 1, characterized in that: The thermistor wires staggered horizontally and vertically in the thermistor network are divided into horizontally distributed thermistor wires and vertically distributed thermistor wires, the spacing between the horizontally distributed thermistor wires is equal, the spacing between the vertically distributed thermistor wires is equal, and the spacing between two adjacent horizontally distributed thermistor wires is equal to the spacing between two adjacent vertically distributed thermistor wires.

5. The monitoring system according to claim 1, characterized in that: During leakage monitoring, the current value measured by the current detection device needs to be corrected for current value deviation before determining whether it exceeds the current variation.

6. The monitoring system according to claim 1, characterized in that: The heat exchanger adopts a single-piece detachable structure, the plate is detachably installed in the frame, the connection parts are on the front and back sides of the frame, and the thermistor network is installed on the plate and located on one side of the plate.

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