Digital judgment method and system for scale cleaning of plate heat exchanger

Abstract

The invention discloses a digital judgment method and system for scale cleaning of a plate heat exchanger, and relates to the technical field of heat supply system heat exchange station equipment. The method includes: acquiring a heat exchanger performance curve; heat supply parameters of real-time operation are obtained; the heat exchange effectiveness epsilon and the total heat transfer coefficient K in the current operation state are calculated; querying a performance curve graph of pressure drop-speed and heat transfer coefficient-speed of the heat exchanger to obtain a corresponding total heat transfer coefficient Ks of the plate heat exchanger in a current running state in a clean state, and calculating a heat exchange effectiveness degree epsilons; and whether the change of the heat exchange effectiveness epsilon and the total heat transfer coefficient K in the current operation state exceeds a preset upper threshold value or not is judged, if yes, it is prompted that the heat exchanger needs to be scaled and cleaned, and if not, data generated in the current operation process is stored. According to the invention, the scaling condition in the heat exchanger can be found comprehensively, accurately and timely, and the digital judgment on the scaling cleaning of the plate heat exchanger is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of heat exchange station equipment of a heating system, and in particular to a digital judgment method and system for scaling cleaning of a plate heat exchanger. Background Art

[0002] The heat exchange station is the hub of the primary and secondary heat networks in the heating system. The plate heat exchanger, as the main equipment of the heat exchange station, plays a role in achieving heat exchange and improving the quality of heating. However, during the long-term heat exchange process, calcium and magnesium ions in the hot water on both sides will precipitate and adhere to the internal plates to form scale. The accumulation of these scales not only significantly reduces the heat transfer efficiency of the heat exchanger and weakens its overall performance, but also increases the flow resistance of the system, resulting in a significant increase in the energy consumption of the water pump while maintaining the same heat exchange rate, causing energy waste.

[0003] Most of the existing technologies for judging the fouling of heat exchangers are passive maintenance solutions that require regular disassembly of the heat exchanger to check for fouling deposition. The disadvantages are that the heat exchanger disassembly operation is cumbersome and the maintenance cost is high; the heating system operation needs to be suspended, affecting the heating service; in addition, these technologies cannot specifically and quantitatively judge the degree of fouling, which often results in the heat exchanger not being cleaned in time, resulting in energy waste and economic losses.

[0004] Therefore, it is an urgent problem for those skilled in the art to propose a digital judgment method and system for plate heat exchanger scaling cleaning to solve the difficulties existing in the prior art. Summary of the invention

[0005] In view of this, the present invention provides a digital judgment method and system for scaling and cleaning of a plate heat exchanger, which can comprehensively, accurately and timely detect the scaling situation inside the heat exchanger and realize digital judgment on scaling and cleaning of the plate heat exchanger.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A digital judgment method for cleaning scale of a plate heat exchanger, comprising:

[0008] S1. Obtaining a performance curve of a plate heat exchanger;

[0009] S2, obtaining the heating parameters of the plate heat exchanger in real time operation;

[0010] S3, calculate the heat exchange effectiveness ε and the total heat transfer coefficient k under the current operating state;

[0011] S4. Query the performance curve of pressure drop-speed and heat transfer coefficient-speed of the plate heat exchanger to obtain the total heat transfer coefficient K corresponding to the plate heat exchanger in the current operating state in the clean state. s , calculate the heat transfer effectiveness εs ;

[0012] S5. Determine whether the changes in the heat exchange effectiveness ε and the total heat transfer coefficient K under the current operating state exceed the preset upper limit threshold. If so, it is prompted that the plate heat exchanger needs to be scaled and cleaned. If not, save the data generated during this operation.

[0013] In the above method, optionally, the performance curve diagram of the plate heat exchanger in S1 includes: a pressure drop-velocity curve diagram and a heat transfer coefficient-velocity curve diagram.

[0014] In the above method, optionally, the heating parameters in S2 include: the temperature, pressure and flow rate of the cold water inlet, the temperature and pressure of the cold water outlet, the temperature, pressure and flow rate of the hot water inlet, and the temperature and pressure of the hot water outlet.

[0015] In the above method, optionally, the heat exchange effectiveness ε in the current operating state in S3 is the ratio of the current heat exchange of the plate heat exchanger to the maximum possible heat exchange, and the calculation formula is:

[0016]

[0017] Where: ΔT 1 ΔT is the temperature difference between the hot water inlet and outlet, in °C; 2 is the temperature difference between the cold water inlet and the cold water outlet, in °C; T 11 is the hot water inlet temperature, in °C; T 21 is the cold water inlet temperature, in °C;

[0018] The total heat transfer coefficient K under the current operating state is calculated from the inlet and outlet parameters of the cold and hot fluids.

[0019] In the above method, optionally, the total heat transfer coefficient K in the clean state is obtained in S4 s , specifically:

[0020] Calculate the pressure difference ΔP between the hot water inlet and outlet of the plate heat exchanger h , cold water inlet and outlet pressure difference ΔP c ;

[0021] Query the pressure drop-velocity curve and heat transfer coefficient-velocity curve of the plate heat exchanger to obtain the total heat transfer coefficient K corresponding to the plate heat exchanger in the current operating state in the clean state s ;

[0022] Calculation of heat transfer effectiveness ε under clean conditions s , specifically:

[0023] Using hot water inlet temperature T 11 , cold water inlet temperature T 21Calculate the hot water outlet temperature T of the plate heat exchanger in a clean state 12 ', cold water outlet temperature T 22 ', the calculation method is as follows:

[0024] K s FΔT' m =C h M h (T 11 -T 12 ')=C c M c (T 22 '-T 21 ) (2)

[0025] Where: C h , C c are the specific heat capacities of hot water and cold water, respectively, in J / (kg·℃); M h 、M c They are hot water flow and cold water flow respectively, in m 3 / h; F is the heat exchange area of ​​the heat exchanger, in m 2 ; ΔT' m is the logarithmic mean temperature difference of the heat exchanger, in °C;

[0026] Formula (2) consists of two equations with two unknowns. The equation has a unique solution. 12 '、T 22 ';

[0027] Heat transfer effectiveness in clean state ε s The calculation formula is:

[0028]

[0029] In the above method, optionally, in S5, the heat transfer effectiveness ε and the total heat transfer coefficient K of the plate heat exchanger in the current operating state are compared with the heat transfer effectiveness ε corresponding to the clean state. s and the total heat transfer coefficient K s Compare and set the upper threshold value according to actual needs.

[0030] A digital judgment system for plate heat exchanger scaling cleaning, which executes any one of the above-mentioned digital judgment methods for plate heat exchanger scaling cleaning, comprising:

[0031] Sensor groups, databases, alarms and online processors;

[0032] A sensor group is connected to the first communication port of the online processor, and is used to obtain the heating parameters of the plate heat exchanger in real time operation, and transmit the heating parameters to the online processor;

[0033] An online processor is used to calculate the scaling index using the received heating parameters, and to determine whether the plate heat exchanger needs scaling cleaning, and to send the determination result to the alarm;

[0034] An alarm, connected to the second communication port of the online processor, for prompting that the heat exchanger needs to be cleaned of fouling;

[0035] A database, connected to the third communication port of the online processor, for storing the process parameters and the judgment results sent by the online processor;

[0036] In the above system, optionally, the sensor group includes: a temperature sensor unit, a flow sensor unit and a pressure sensor unit; wherein,

[0037] The temperature sensor unit consists of:

[0038] The first temperature sensor is arranged on the pipe of the cold water inlet of the plate heat exchanger and is used to measure the temperature at the cold water inlet;

[0039] The second temperature sensor is arranged on the pipe of the cold water outlet of the plate heat exchanger and is used to measure the temperature at the hot water outlet;

[0040] A third temperature sensor is provided on the pipe of the hot water inlet of the plate heat exchanger and is used to measure the temperature at the hot water inlet;

[0041] The fourth temperature sensor is arranged on the pipe of the hot water outlet of the plate heat exchanger and is used to measure the temperature at the cold water outlet;

[0042] The flow sensor unit consists of:

[0043] A first flow sensor is provided on the pipe of the cold water inlet of the plate heat exchanger and is used to measure the flow at the cold water inlet;

[0044] A second flow sensor is provided on the pipe of the hot water inlet of the plate heat exchanger and is used to measure the flow at the hot water inlet;

[0045] The pressure sensor unit consists of:

[0046] The first pressure sensor is arranged on the pipe of the cold water inlet of the plate heat exchanger and is used to measure the pressure at the cold water inlet;

[0047] The second pressure sensor is arranged on the pipe of the cold water outlet of the plate heat exchanger and is used to measure the pressure at the cold water outlet;

[0048] A third pressure sensor is provided on the pipe of the hot water inlet of the plate heat exchanger and is used to measure the pressure at the hot water inlet;

[0049] The fourth pressure sensor is arranged on the pipe of the hot water outlet of the plate heat exchanger and is used to measure the pressure at the hot water outlet.

[0050] It can be seen from the above technical solution that, compared with the prior art, the present invention provides a digital judgment method and system for cleaning of plate heat exchanger fouling, which has the following beneficial effects: the present invention is based on real-time monitoring of operating data, does not rely on manual experience and regular cleaning and maintenance methods, and effectively monitors whether the plate heat exchanger needs to be cleaned in real time to ensure efficient and stable operation of the heat exchanger; uses performance indicators from different angles to measure the fouling of the plate heat exchanger, can comprehensively, accurately and timely discover the fouling inside the heat exchanger, and quantify it, and more intuitively display and understand the impact of heat exchanger fouling on the heat exchange performance of the plate heat exchanger; the implementation is simple and reliable, not only suitable for newly built heat exchange stations, but also can be used in the digital transformation of existing heat exchange stations, and the online processor can send the status of the plate heat exchanger to the alarm in time through a wireless connection, which can better ensure the safety of the system. 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 for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0052] Figure 1 A flow chart of a digital determination method for scaling and cleaning of a plate heat exchanger provided by the present invention;

[0053] Figure 2 A structural diagram of a digital judgment system for plate heat exchanger scaling cleaning provided by the present invention;

[0054] Description of reference numerals:

[0055] 1 is the cold water inlet; 2 is the cold water outlet; 3 is the hot water inlet; 4 is the hot water outlet; 5 is the first temperature sensor; 6 is the first flow sensor; 7 is the first pressure sensor; 8 is the second temperature sensor; 9 is the second pressure sensor; 10 is the third pressure sensor; 11 is the second flow sensor; 12 is the third temperature sensor; 13 is the fourth pressure sensor; 14 is the fourth temperature sensor; 15 is the alarm; 16 is the online processor; 17 is the database; 18 is the plate heat exchanger. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] In this application, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, the elements defined by the sentence "comprise one..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0058] Reference Figure 1 and Figure 2 As shown, the present invention discloses a digital judgment method for cleaning scale of a plate heat exchanger, comprising:

[0059] S1, obtaining a performance curve diagram of the plate heat exchanger 18;

[0060] S2, obtaining the heating parameters of the plate heat exchanger 18 in real time operation;

[0061] S3, calculate the heat exchange effectiveness ε and the total heat transfer coefficient K under the current operating state;

[0062] S4. Query the performance curve of the pressure drop-speed and heat transfer coefficient-speed of the plate heat exchanger 18 to obtain the total heat transfer coefficient K corresponding to the plate heat exchanger 18 in the current operating state in the clean state. s , calculate the heat transfer effectiveness ε s ;

[0063] S5. Determine whether the changes in the heat exchange effectiveness ε and the total heat transfer coefficient K under the current operating state exceed the preset upper limit threshold. If so, it is prompted that the plate heat exchanger 18 needs to be scaled and cleaned. If not, save the data generated during this operation.

[0064] Furthermore, the performance curve diagram of the plate heat exchanger 18 in S1 includes: a pressure drop-velocity curve diagram and a heat transfer coefficient-velocity curve diagram.

[0065] Furthermore, the heating parameters in S2 include: the temperature, pressure and flow rate of the cold water inlet 1 , the temperature and pressure of the cold water outlet 2 , the temperature, pressure and flow rate of the hot water inlet 3 , and the temperature and pressure of the hot water outlet 4 .

[0066] Furthermore, the heat exchange effectiveness ε in the current operating state in S3 is the ratio of the current heat exchange of the plate heat exchanger 18 to the maximum possible heat exchange, and the calculation formula is:

[0067]

[0068] Where: ΔT 1 is the temperature difference between the hot water inlet 3 and the hot water outlet 4, in °C; ΔT 2 is the temperature difference between cold water inlet 1 and cold water outlet 2, in °C; T 11 is the hot water inlet 3 temperature, in °C; T 21 is the cold water inlet 1 temperature, in °C;

[0069] The total heat transfer coefficient K under the current operating state is calculated from the inlet and outlet parameters of the cold and hot fluids.

[0070] Furthermore, the total heat transfer coefficient K in the clean state is obtained in S4 s , specifically:

[0071] Calculate the pressure difference ΔP between the hot water inlet 3 and the hot water outlet 4 of the plate heat exchanger 18 h , cold water inlet 1 and cold water outlet 2 pressure difference ΔP c ;

[0072] Query the pressure drop-velocity curve and heat transfer coefficient-velocity curve of the plate heat exchanger 18 to obtain the total heat transfer coefficient K corresponding to the plate heat exchanger 18 in the current operating state in the clean state. s ;

[0073] Calculation of heat transfer effectiveness ε under clean conditions s , specifically:

[0074] Using hot water inlet 3 temperature T 11 , Cold water inlet 1 temperature T 21 Calculate the hot water outlet 4 temperature T corresponding to the plate heat exchanger 18 in the clean state 12 ', cold water outlet 2 temperature T 22 ', the calculation method is as follows:

[0075] K s FΔT' m =C h M h (T 11 -T 12 ')=C c Mc (T 22 '-T 21 ) (2)

[0076] Where: C h , C c are the specific heat capacities of hot water and cold water, respectively, in J / (kg·℃); M h 、M c They are hot water flow and cold water flow respectively, in m 3 / h; F is the heat exchange area of ​​the heat exchanger, in m 2 ; ΔT' m is the logarithmic mean temperature difference of the heat exchanger, in °C;

[0077] Formula (2) consists of two equations with two unknowns. The equation has a unique solution. 12 '、T 22 ';

[0078] Heat transfer effectiveness in clean state ε s The calculation formula is:

[0079]

[0080] Further, in S5, the heat exchange effectiveness ε and the total heat transfer coefficient K of the plate heat exchanger 18 in the current operating state are compared with the heat exchange effectiveness ε corresponding to the clean state. s and the total heat transfer coefficient K s Compare and set the upper threshold value according to actual needs.

[0081] Reference Figure 2 As shown, a plate heat exchanger scaling cleaning digital judgment system executes any one of the above-mentioned plate heat exchanger scaling cleaning digital judgment methods, including:

[0082] Sensor group, database 17, alarm 15 and online processor 16;

[0083] A sensor group connected to the first communication port of the online processor 16, used to obtain the heating parameters of the plate heat exchanger 18 in real time operation and transmit the heating parameters to the online processor 16;

[0084] The online processor 16 is used to calculate the scaling index using the received heating parameters, and determine whether the plate heat exchanger 18 needs scaling cleaning, and send the determination result to the alarm 15;

[0085] An alarm 15 is connected to the second communication port of the online processor 16 and is used to prompt that the heat exchanger needs to be cleaned of scale;

[0086] The database 17 is connected to the third communication port of the online processor 16 and is used to store the process parameters sent by the online processor 16 and the judgment results.

[0087] Furthermore, the sensor group includes: a temperature sensor unit, a flow sensor unit and a pressure sensor unit; wherein,

[0088] The temperature sensor unit consists of:

[0089] The first temperature sensor 5 is arranged on the pipe of the cold water inlet 1 of the plate heat exchanger 18, and is used to measure the temperature at the cold water inlet 1;

[0090] The second temperature sensor 8 is arranged on the pipe of the cold water outlet 2 of the plate heat exchanger 18 and is used to measure the temperature at the hot water outlet 4;

[0091] The third temperature sensor 12 is arranged on the pipe of the hot water inlet 3 of the plate heat exchanger 18, and is used to measure the temperature at the hot water inlet 3;

[0092] The fourth temperature sensor 14 is arranged on the pipe of the hot water outlet 4 of the plate heat exchanger 18 and is used to measure the temperature at the cold water outlet 2;

[0093] The flow sensor unit consists of:

[0094] The first flow sensor 6 is arranged on the pipe of the cold water inlet 1 of the plate heat exchanger 18 and is used to measure the flow at the cold water inlet 1;

[0095] The second flow sensor 11 is arranged on the pipe of the hot water inlet 3 of the plate heat exchanger 18, and is used to measure the flow at the hot water inlet 3;

[0096] The pressure sensor unit consists of:

[0097] The first pressure sensor 7 is arranged on the pipe of the cold water inlet 1 of the plate heat exchanger 18, and is used to measure the pressure at the cold water inlet 1;

[0098] The second pressure sensor 9 is arranged on the pipe of the cold water outlet 2 of the plate heat exchanger 18, and is used to measure the pressure at the cold water outlet 2;

[0099] The third pressure sensor 10 is arranged on the pipe of the hot water inlet 3 of the plate heat exchanger 18, and is used to measure the pressure at the hot water inlet 3;

[0100] The fourth pressure sensor 13 is disposed on the pipeline of the hot water outlet 4 of the plate heat exchanger 18 and is used to measure the pressure at the hot water outlet 4 .

[0101] In a specific embodiment, the first temperature sensor 5, the second temperature sensor 8, the third temperature sensor 12 and the fourth temperature sensor 14 are all thermocouple thermometers, and the temperature measurement range is -50°C to 200°C. The thermocouple temperature sensors can be better replaced and maintained;

[0102] The first temperature sensor 5, the second temperature sensor 8, the third temperature sensor 12 and the fourth temperature sensor 14 are all arranged at a distance of three times the pipe diameter from the heat exchanger. At least two temperature sensors are arranged on each connecting main pipe and fastened with clamps. The distance between the temperature sensors is more than two times the pipe diameter.

[0103] The first flow sensor 6 and the second flow sensor 11 are both flange-type ultrasonic flow sensors;

[0104] All sensors are connected to the wireless connector, and the wireless connector is connected to the online processor 16. When in use, the sensors transmit data to the online processor 16 through the wireless connector by wireless transmission.

[0105] In another specific embodiment, the online processor 16 is used to obtain the real-time operating temperature, pressure and flow rate of the hot water inlet 3, the hot water outlet 4 and the cold water inlet 1, the cold water outlet 2 of the plate heat exchanger 18, calculate the real-time operating heat exchange effectiveness ε and the total heat transfer coefficient K of the plate heat exchanger 18, and find the total heat transfer coefficient K of the plate heat exchanger 18 under the current cleaning condition according to the performance curve diagram of the plate heat exchanger 18 stored in the database 17. s And calculate the heat transfer effectiveness ε under the current working condition clean conditions s , Comparison of fouling indicators: heat transfer effectiveness percentage change Overall heat transfer coefficient change percentage The comparison result is related to the size of the preset upper threshold, and whether the plate heat exchanger needs to be cleaned; the upper threshold is set to 20% here. If it exceeds the upper threshold, the online processor 16 controls the alarm 15 to alarm, outputs a prompt message, prompts that the heat exchanger is severely scaled and needs to be cleaned, and saves the data to the database 17; if it does not exceed the upper threshold, the data generated during this operation is saved to the database 17.

[0106] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can refer to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment. The system and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without creative work.

[0107] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A digital judgment method for plate heat exchanger scaling cleaning, characterized in that: include: S1. Obtaining a performance curve of a plate heat exchanger; S2, obtaining the heating parameters of the plate heat exchanger in real time operation; S3, calculate the heat exchange effectiveness ε and the total heat transfer coefficient K under the current operating state; S4. Query the performance curve of pressure drop-speed and heat transfer coefficient-speed of the plate heat exchanger to obtain the total heat transfer coefficient K corresponding to the plate heat exchanger in the current operating state in the clean state. s , calculate the heat transfer effectiveness ε s ; S5. Determine whether the changes in the heat exchange effectiveness ε and the total heat transfer coefficient K under the current operating state exceed the preset upper limit threshold. If so, it is prompted that the plate heat exchanger needs to be scaled and cleaned. If not, save the data generated during this operation.

2. A digital judgment method for plate heat exchanger scaling cleaning according to claim 1, characterized in that: The performance curves of the plate heat exchanger in S1 include: pressure drop-velocity curve and heat transfer coefficient-velocity curve.

3. A digital determination method for plate heat exchanger fouling cleaning according to claim 1, characterized in that: The heating parameters in S2 include: the temperature, pressure and flow rate of the cold water inlet, the temperature and pressure of the cold water outlet, the temperature, pressure and flow rate of the hot water inlet, and the temperature and pressure of the hot water outlet.

4. A digital determination method for plate heat exchanger fouling cleaning according to claim 1, characterized in that: The heat exchange effectiveness ε in the current operating state in S3 is the ratio of the current heat exchange of the plate heat exchanger to the maximum possible heat exchange, and the calculation formula is: Where: ΔT1 is the temperature difference between the hot water inlet and the hot water outlet, in °C; ΔT2 is the temperature difference between the cold water inlet and the cold water outlet, in °C; T 11 is the hot water inlet temperature, in °C; T 21 is the cold water inlet temperature, in °C; The total heat transfer coefficient K under the current operating state is calculated from the inlet and outlet parameters of the cold and hot fluids.

5. A digital determination method for plate heat exchanger fouling cleaning according to claim 1, characterized in that: The total heat transfer coefficient K in the clean state is obtained in S4 s , specifically: Calculate the pressure difference ΔP between the hot water inlet and outlet of the plate heat exchanger h , cold water inlet and outlet pressure difference ΔP c ; Query the pressure drop-velocity curve and heat transfer coefficient-velocity curve of the plate heat exchanger to obtain the total heat transfer coefficient K corresponding to the plate heat exchanger in the current operating state in the clean state s ; Calculation of heat transfer effectiveness ε under clean conditions s , specifically: Using hot water inlet temperature T 11 , cold water inlet temperature T 21 Calculate the hot water outlet temperature T of the plate heat exchanger in a clean state 12 ', cold water outlet temperature T 22 ', the calculation method is as follows: K s FΔT' m =C h M h (T 11 -T 12 ')=C c M c (T 22 '-T 21 ) (2) Where: C h , C c are the specific heat capacities of hot water and cold water, respectively, in J / (kg·℃); M h 、M c They are hot water flow and cold water flow respectively, in m 3 / h; F is the heat exchange area of ​​the heat exchanger, in m 2 ; ΔT' m is the logarithmic mean temperature difference of the heat exchanger, in °C; Formula (2) consists of two equations with two unknowns. The equation has a unique solution. 12 '、T 22 '; Heat transfer effectiveness in clean state ε s The calculation formula is:

6. A digital determination method for plate heat exchanger fouling cleaning according to claim 1, characterized in that: In S5, the heat transfer effectiveness ε and the total heat transfer coefficient K of the plate heat exchanger in the current operating state are compared with the heat transfer effectiveness ε corresponding to the clean state. s and the total heat transfer coefficient K s Compare and set the upper threshold value according to actual needs.

7. A digital judgment system for plate heat exchanger scaling cleaning, characterized in that: A digital determination method for cleaning plate heat exchanger fouling according to any one of claims 1 to 6, comprising: Sensor groups, databases, alarms and online processors; A sensor group is connected to the first communication port of the online processor, and is used to obtain the heating parameters of the plate heat exchanger in real time operation, and transmit the heating parameters to the online processor; An online processor is used to calculate the scaling index using the received heating parameters, and to determine whether the plate heat exchanger needs scaling cleaning, and to send the determination result to the alarm; An alarm, connected to the second communication port of the online processor, for prompting that the heat exchanger needs to be cleaned of fouling; The database is connected to the third communication port of the online processor and is used to store the process parameters and judgment results sent by the online processor.

8. A plate heat exchanger scaling cleaning digital judgment system according to claim 7, characterized in that: The sensor group includes: a temperature sensor unit, a flow sensor unit and a pressure sensor unit; wherein, The temperature sensor unit consists of: The first temperature sensor is arranged on the pipe of the cold water inlet of the plate heat exchanger and is used to measure the temperature at the cold water inlet; The second temperature sensor is arranged on the pipe of the cold water outlet of the plate heat exchanger and is used to measure the temperature at the hot water outlet; A third temperature sensor is provided on the pipe of the hot water inlet of the plate heat exchanger and is used to measure the temperature at the hot water inlet; The fourth temperature sensor is arranged on the pipe of the hot water outlet of the plate heat exchanger and is used to measure the temperature at the cold water outlet; The flow sensor unit consists of: A first flow sensor is provided on the pipe of the cold water inlet of the plate heat exchanger and is used to measure the flow at the cold water inlet; A second flow sensor is provided on the pipe of the hot water inlet of the plate heat exchanger and is used to measure the flow at the hot water inlet; The pressure sensor unit consists of: The first pressure sensor is arranged on the pipe of the cold water inlet of the plate heat exchanger and is used to measure the pressure at the cold water inlet; The second pressure sensor is arranged on the pipe of the cold water outlet of the plate heat exchanger and is used to measure the pressure at the cold water outlet; A third pressure sensor is provided on the pipe of the hot water inlet of the plate heat exchanger and is used to measure the pressure at the hot water inlet; The fourth pressure sensor is arranged on the pipe of the hot water outlet of the plate heat exchanger and is used to measure the pressure at the hot water outlet.

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