Automatic control method and system for freezing prevention of plate heat exchanger of cooling-water machine

Abstract

The invention discloses an automatic anti-freezing control method and system for a plate heat exchanger of a cooling-water machine, relates to the technical field of cooling-water machines, and aims to solve the problem that an existing anti-freezing control method for the plate heat exchanger does not have universal adaptability. The method comprises the steps that S1, temperature data of a refrigerant side and a circulating liquid side and exhaust and air return pressure of a refrigerant are obtained; s2, whether the outlet water temperature of the circulating liquid side is smaller than or equal to a circulating liquid threshold value d or not is judged, if yes, an anti-freezing mechanism is operated, and if not, normal shutdown is initially executed, and S3 is executed; s3, whether the outlet water temperature of the refrigerant side is larger than a refrigerant threshold value g1 or not is judged, and if yes, the step S4 is executed; if not, whether the water inlet temperature of the refrigerant side is smaller than or equal to g1 or not is judged, if yes, an anti-freezing mechanism is operated, and if not, continuous detection is conducted; s4, whether the water inlet temperature of the refrigerant side is larger than g1 or not is judged; and if yes, ending, and if not, carrying out warning judgment. The temperature data of the refrigerant side and the circulating liquid side are judged to achieve comprehensive and automatic control over freezing prevention of the plate heat exchanger.

Description

Technical Field

[0001] This invention relates to the field of chiller technology, specifically to an automatic control method and system for preventing the plate heat exchanger of a chiller from freezing. Background Technology

[0002] Chillers are devices designed to ensure that precision instruments operate under constant temperature conditions. Plate heat exchangers are key components in chillers, responsible for heat exchange between chilled water and refrigerant. Freezing of the plate heat exchanger or chilled water can lead to a decrease in the machine's cooling capacity or even damage to the chiller.

[0003] Currently, common anti-freeze control methods on the market involve manual control or using an ambient temperature sensor to circulate the water pump to prevent chilled water from freezing. These methods primarily prevent chilled water freezing caused by the ambient temperature being lower than the freezing point of the chilled water. However, besides the common causes of chilled water freezing, a special case is easily overlooked: at low outlet water temperatures, the temperature of the refrigerant in the plate heat exchanger is lower than the freezing point of the chilled water. While the chiller pump is running, the circulation of chilled water and the heat load do not cause freezing. However, when the system is shut down, the pump stops, and the chilled water stops flowing. At this point, the temperature of the refrigerant in the plate heat exchanger remains lower than the freezing point of the chilled water, leading to freezing of the chilled water inside the plate heat exchanger. Chinese patent CN117109353A, which only controls the operation of the water pump and the electrically controlled two-way valve assembly based on the temperature of the plate heat exchanger and the ambient temperature, lacks general applicability. Summary of the Invention

[0004] This invention solves the problem that current antifreeze control methods for plate heat exchangers lack universal applicability. It proposes an automatic control method and system for antifreeze of plate heat exchangers in chillers. By judging the temperature data of the refrigerant side and the circulating liquid side and through a multi-stage warning judgment process, combined with future set cycle or historical time period data, the antifreeze of the plate heat exchanger is fully automatically controlled.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: an automatic control method for antifreeze of a plate heat exchanger in a chiller, comprising the following steps: S1, acquire the refrigerant side and circulating liquid side temperature data of the plate heat exchanger, and the exhaust and return pressure of the refrigerant; S2, determine whether the outlet water temperature on the circulating fluid side is less than or equal to the circulating fluid threshold d. If yes, run the antifreeze mechanism. If no, perform a normal shutdown and proceed to S3. S3, determine whether the outlet water temperature on the refrigerant side is greater than the refrigerant threshold g1. If yes, proceed to S4; if no, determine whether the inlet water temperature on the refrigerant side is less than or equal to g1. If yes, run the antifreeze mechanism; if no, continue monitoring. S4, determine if the inlet water temperature on the refrigerant side is greater than g1; if yes, end the process; otherwise, issue a warning.

[0006] First, temperature and pressure data are acquired. After obtaining the relevant temperature and pressure data, the relationship between the outlet water temperature on the circulating liquid side of the plate heat exchanger and the set circulating liquid threshold is determined. If the outlet water temperature on the circulating liquid side of the plate heat exchanger is less than or equal to the circulating liquid threshold d, the antifreeze mechanism is directly activated. If the outlet water temperature is greater than the circulating liquid threshold d, the refrigerant side of the plate heat exchanger is detected and judged. The relationship between the outlet water temperature on the refrigerant side of the plate heat exchanger and the set refrigerant threshold is judged. If the outlet water temperature on the refrigerant side of the plate heat exchanger is greater than g1, the relationship between the inlet water temperature on the refrigerant side and g1 is further judged. If it is greater than g1, the entire process ends normally. If it is less than or equal to g1, an alarm judgment is made. If the outlet water temperature on the refrigerant side of the plate heat exchanger is less than or equal to g1, the inlet water temperature on the refrigerant side is judged again. If it is, the antifreeze mechanism is run. The judgment process of this invention can handle various situations of the chiller plate heat exchanger, and the entire process is automatic judgment and control.

[0007] The present invention is further configured such that the antifreeze mechanism specifically comprises: The entire refrigeration system shuts down, but the water pump connected to the circulating liquid inlet of the plate heat exchanger continues to run until the refrigerant discharge pressure equals the refrigerant return pressure.

[0008] In this technical solution, the plate heat exchanger can be protected from freezing through the above process. The power of the water pump can be adjusted according to the actual situation.

[0009] The present invention is further configured such that the warning judgment specifically includes: Calculate the difference between the outlet water temperature and the inlet water temperature on the refrigerant side at real time to obtain the first difference value, and set the maximum antifreeze temperature difference value. Determine whether the first difference value is greater than the maximum antifreeze temperature difference value. If it is, adjust the electronic expansion valve connected to the refrigerant side inlet of the plate heat exchanger. If not, run the antifreeze mechanism after a set interval.

[0010] In this technical solution, warning judgment is used to further ensure the prevention of freezing of plate heat exchangers.

[0011] The present invention is further configured such that: in step S3, when the inlet water temperature on the refrigerant side is greater than g1, the difference between the inlet water temperature on the refrigerant side and g1 is determined; if the difference is less than the warning temperature difference, the collection and comparison of temperature data and pressure data are accelerated, and the process is returned to S2 based on the temperature data.

[0012] In this technical solution, when the outlet water temperature on the refrigerant side is less than g1 and the inlet water temperature on the refrigerant side is greater than g1, since the specific value of the inlet water temperature on the refrigerant side exceeding g1 is not clear in a short time, it is necessary to make further judgments based on the warning temperature difference.

[0013] The present invention is further configured such that: if the difference between the inlet water temperature on the refrigerant side and g1 is greater than the warning temperature difference, the process directly returns to step S1 and performs detection according to the original collection cycle.

[0014] In this technical solution, if the difference is outside the warning temperature difference, no additional acceleration processing is required.

[0015] The present invention is further configured such that: in step S4, if the inlet water temperature on the refrigerant side is greater than g1, it is initially determined that a normal shutdown will be performed, and further judgment will be made through a future set cycle: the inlet water temperature and outlet water temperature on the refrigerant side within the future set cycle will be continuously judged against g1 to determine whether there is a situation where the inlet water temperature or outlet water temperature on the refrigerant side does not meet the condition of being greater than g1 within the future set cycle. If so, it is also necessary to switch to the warning judgment process.

[0016] The present invention is further configured such that: in step S4, if the inlet water temperature on the refrigerant side is greater than g1, a normal shutdown is initially determined, and further judgment is made using historical time period data: a historical time period database is created for this condition, the corresponding historical time period data is retrieved according to the determined historical time period, the cases in which the inlet water temperature or outlet water temperature on the refrigerant side in the historical time period data does not meet the condition of being greater than g1 are statistically analyzed, and whether to switch to the warning judgment process is determined according to the time difference between the historical time period and the current time period.

[0017] The present invention is further configured such that: the step of determining whether to enter the warning judgment process based on the time difference between the historical time period and the current time period specifically includes: creating a mapping model between the time difference between the historical time period and the current time period and the judgment accuracy of the current time period, wherein each time difference corresponds to a judgment accuracy range for a time period, and determining whether the judgment of the current time period is within the judgment accuracy standard range for the time period based on the time difference.

[0018] The present invention is further configured such that: the temperature data of the refrigerant side and the circulating liquid side of the plate heat exchanger are obtained by temperature acquisition devices of the refrigerant side and the circulating liquid side; and the exhaust and return pressures of the refrigerant are obtained by pressure acquisition devices.

[0019] In this technical solution, relevant data are collected based on temperature and pressure sensors.

[0020] A control optimization system based on a cold plate temperature conduction hysteresis system, applicable to the aforementioned control optimization method based on a cold plate temperature conduction hysteresis system, includes a central control center for recording process data and sending commands. The central control center is connected to a data acquisition module, which can acquire data from temperature acquisition devices and pressure acquisition devices. The data acquisition module is connected to a temperature judgment module, which is connected to a mechanism selection module.

[0021] The central control center, data acquisition module, temperature judgment module, and mechanism selection module are connected in sequence to achieve comprehensive automatic control of plate heat exchanger antifreeze.

[0022] The present invention can bring the following beneficial effects: This application discloses an automatic control method for preventing freezing of plate heat exchangers in chillers. It outlines a process for judging temperature data on the refrigerant side and circulating liquid side, as well as a warning judgment process. This method can handle various situations of plate heat exchangers in chillers. The entire process is automatic, requiring no human intervention. It can significantly improve the performance and reliability of chillers. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the application scenario of the automatic control method for preventing freezing of a plate heat exchanger in a chiller, as described in this application.

[0024] Figure 2 This is a partial flowchart illustrating an automatic control method for preventing freezing of a plate heat exchanger in a chiller, as described in this application.

[0025] Figure 3 This is a schematic diagram of an automatic control system for preventing freezing of a plate heat exchanger in a chiller, as described in this application.

[0026] Attached reference numerals: 1. Plate heat exchanger; 2. Water pump; 3. Outlet water temperature sensor; 4. Water pressure sensor; 5. Return water temperature sensor; 6. Liquid level switch; 7. Customer heat source; 8. Drain outlet; 9. Dryer filter; 10. First electronic expansion valve. 11. Second electronic expansion valve; 12. First pressure sensor; 13. Exhaust temperature sensor; 14. Second pressure sensor; 15. Return gas temperature sensor; 16. Compressor; 17. Cooling water outlet; 18. Cooling water inlet; 19. Condenser. Detailed Implementation

[0027] Example 1 This embodiment proposes an automatic control method for antifreeze protection of plate heat exchangers in chillers, referring to... Figure 2 It mainly includes the following steps.

[0028] Step S1: First, obtain the temperature data of the plate heat exchanger on the refrigerant side and the circulating liquid side, and at the same time obtain the exhaust and return gas pressures on the refrigerant side.

[0029] For step S1 above, the temperature data of the refrigerant side and the circulating liquid side of the plate heat exchanger are obtained by temperature acquisition devices installed on the refrigerant side and the circulating liquid side, and the exhaust and return gas pressures of the refrigerant side are obtained by pressure acquisition devices.

[0030] In this embodiment, the temperature acquisition device is a temperature sensor, and the pressure acquisition device is a pressure sensor. Of course, other devices can also be used, and no limitation is made here.

[0031] In this embodiment, data is collected using temperature and pressure sensors.

[0032] Step S2: After completing the above data acquisition steps, further determine the relationship between the outlet water temperature c on the circulating fluid side and the circulating fluid threshold d. If the outlet water temperature c on the circulating fluid side is less than or equal to the circulating fluid threshold d, the antifreeze mechanism should be activated immediately. If the outlet water temperature c on the circulating fluid is greater than the circulating fluid threshold d, it is considered to be initially normal and a normal shutdown can be performed, but further judgment is still required.

[0033] The aforementioned antifreeze mechanism process is as follows: the entire refrigeration system is shut down, but the water pump continues to run. This water pump is connected to the inlet of the circulating liquid side of the plate heat exchanger, and the water pump continues to run until the exhaust pressure on the refrigerant side is equal to the return pressure on the refrigerant side.

[0034] In this embodiment, the plate heat exchanger can be protected from freezing through the above process. The power of the water pump can be adjusted according to the actual situation. Generally, the above-mentioned antifreeze mechanism should be implemented immediately.

[0035] Step S3: Further determine the relationship between the outlet water temperature e on the refrigerant side of the plate heat exchanger and the set refrigerant threshold g1. If the outlet water temperature e on the refrigerant side of the plate heat exchanger is greater than the set refrigerant threshold g1, proceed to step S4. If the outlet water temperature e on the refrigerant side of the plate heat exchanger is less than or equal to the set refrigerant threshold g1, further determine the relationship between the inlet water temperature f on the refrigerant side of the plate heat exchanger and the set refrigerant threshold g1. If the inlet water temperature f on the refrigerant side of the plate heat exchanger is less than or equal to the set refrigerant threshold g1, the antifreeze mechanism should be activated. If the inlet water temperature f on the refrigerant side of the plate heat exchanger is greater than the refrigerant threshold g1, continuous monitoring should be performed.

[0036] In step S3, specifically when the inlet water temperature f on the refrigerant side of the plate heat exchanger is greater than the set refrigerant threshold g1, the difference between the inlet water temperature f and the set refrigerant threshold can be further determined, and the relationship between this difference and the set warning temperature difference can be determined. If this difference is less than the warning temperature difference, it means that although the inlet water temperature f on the refrigerant side of the plate heat exchanger is greater than the refrigerant threshold g1, the outlet water temperature e on the refrigerant side of the plate heat exchanger is also less than the set refrigerant threshold g1 in this case. In addition, the inlet water temperature f on the refrigerant side of the plate heat exchanger is still within the warning temperature difference range above the critical value. Therefore, the collection and comparison of temperature and pressure data should be accelerated, and the process should return to S2 based on the temperature data.

[0037] In this embodiment, when the outlet water temperature on the refrigerant side is less than g1 and the inlet water temperature on the refrigerant side is greater than g1, since the specific value of the inlet water temperature on the refrigerant side exceeding g1 is not clear in a short time, it is necessary to make a further judgment based on the warning temperature difference.

[0038] Based on the above judgment, if the difference between the inlet water temperature f and the refrigerant threshold g1 is greater than the above warning temperature difference, then there is no need to accelerate the collection and comparison process. Instead, the process returns directly to step S1 and performs detection and subsequent judgment according to the original collection cycle.

[0039] In this embodiment, if the difference is outside the warning temperature difference, no additional acceleration processing is required.

[0040] Step S4: After completing step S3, further determine the relationship between the inlet water temperature on the refrigerant side of the plate heat exchanger and the set refrigerant threshold g1. If the inlet water temperature on the refrigerant side of the plate heat exchanger is greater than the set refrigerant threshold g1, the entire control judgment process can be terminated. If the inlet water temperature on the refrigerant side of the plate heat exchanger is less than or equal to the set refrigerant threshold g1, an alarm judgment process will be initiated immediately.

[0041] The aforementioned warning judgment process mainly includes the following steps: First, calculate the instantaneous outlet water temperature on the refrigerant side and the inlet water temperature on the refrigerant side of the plate heat exchanger, and calculate the difference between the two to obtain the first difference value. At the same time, set the maximum value of the antifreeze temperature difference. The set antifreeze temperature difference has a standard range, and the maximum value is taken here. Determine the relationship between the first difference value and the maximum value of the antifreeze temperature difference. If the first difference value is greater than the maximum value of the antifreeze temperature difference, the electronic expansion valve should be adjusted. This electronic expansion valve is connected to the refrigerant side inlet of the plate heat exchanger. If the first difference value is less than or equal to the maximum value of the antifreeze temperature difference, the antifreeze mechanism will be activated after a set interval.

[0042] In this embodiment, warning judgment is used to further ensure the prevention of freezing of the plate heat exchanger.

[0043] In step S4, the following further judgment can be selectively performed: when the inlet water temperature f on the refrigerant side of the plate heat exchanger is greater than the set refrigerant threshold g1, it can be preliminarily determined that a normal shutdown will be performed subsequently. In this embodiment, in order to ensure further precise control of the chiller plate heat exchanger, further judgment is made in conjunction with the future set cycle.

[0044] The specific process is as follows: After setting the future set period, extract the inlet water temperature f and outlet water temperature e of the refrigerant side of the plate heat exchanger within the future set period. Continuously compare the inlet water temperature f and outlet water temperature e with the set refrigerant threshold g1 within the set refrigerant threshold g1 multiple times to determine if there are any cases where the inlet water temperature or outlet water temperature on the refrigerant side does not exceed g1 within the future set period. If there are cases where the inlet water temperature f or outlet water temperature e of the plate heat exchanger is less than or equal to the set refrigerant threshold g1, then the process needs to proceed to the aforementioned warning judgment procedure. If there are no cases where the inlet water temperature f or outlet water temperature e of the plate heat exchanger is less than or equal to the set refrigerant threshold g1, then it is ultimately determined that a normal shutdown operation will be performed.

[0045] First, temperature and pressure data are acquired. After obtaining the relevant temperature and pressure data, the relationship between the outlet water temperature on the circulating liquid side of the plate heat exchanger and the set circulating liquid threshold is determined. If the outlet water temperature on the circulating liquid side of the plate heat exchanger is less than or equal to the circulating liquid threshold d, the antifreeze mechanism is directly activated. If the outlet water temperature is greater than the circulating liquid threshold d, the refrigerant side of the plate heat exchanger is detected and judged. The relationship between the outlet water temperature on the refrigerant side of the plate heat exchanger and the set refrigerant threshold is judged. If the outlet water temperature on the refrigerant side of the plate heat exchanger is greater than g1, the relationship between the inlet water temperature on the refrigerant side and g1 is further judged. If it is greater than g1, the entire process ends normally. If it is less than or equal to g1, an alarm judgment is made. If the outlet water temperature on the refrigerant side of the plate heat exchanger is less than or equal to g1, the inlet water temperature on the refrigerant side is judged again. If it is, the antifreeze mechanism is run. The judgment process of this invention can handle various situations of the chiller plate heat exchanger, and the entire process is automatic judgment and control.

[0046] The above process can bring about the following technical effects: 1. Intelligent automatic judgment and control without human intervention; 2. Improved performance and reliability of related products; 3. Reduced use of special liquids and reduced costs, depending on the situation.

[0047] Based on the above-described automatic control method for antifreeze protection of plate heat exchangers in chillers, this embodiment also proposes an automatic control system for antifreeze protection of plate heat exchangers in chillers, referencing... Figure 3It mainly includes a central control center, a data acquisition module, a temperature judgment module, and a mechanism selection module. The central control center, data acquisition module, temperature judgment module, and mechanism selection module are connected in sequence to jointly realize the comprehensive automatic control of plate heat exchanger antifreeze.

[0048] The main functions of the central control center are to record process data and send specific start or end commands.

[0049] The data acquisition module can be connected to the temperature acquisition device and the pressure acquisition device, and can acquire the data from the temperature acquisition device and the pressure acquisition device in a timely manner.

[0050] The temperature judgment module is responsible for performing the judgment process from steps S2 to S4 above.

[0051] The mechanism selection module determines whether to run the antifreeze mechanism.

[0052] Example 2 This embodiment proposes an automatic control method for preventing freezing of plate heat exchangers in chillers, which mainly includes the following steps.

[0053] Step S1: First, obtain the temperature data of the plate heat exchanger on the refrigerant side and the circulating liquid side, and at the same time obtain the exhaust and return gas pressures on the refrigerant side.

[0054] For step S1 above, the temperature data of the refrigerant side and the circulating liquid side of the plate heat exchanger are obtained by temperature acquisition devices installed on the refrigerant side and the circulating liquid side, and the exhaust and return gas pressures of the refrigerant side are obtained by pressure acquisition devices.

[0055] Step S2: After completing the above data acquisition steps, further determine the relationship between the outlet water temperature c on the circulating fluid side and the circulating fluid threshold d. If the outlet water temperature c on the circulating fluid side is less than or equal to the circulating fluid threshold d, the antifreeze mechanism should be activated immediately. If the outlet water temperature c on the circulating fluid is greater than the circulating fluid threshold d, it is considered to be initially normal and a normal shutdown can be performed, but further judgment is still required.

[0056] The aforementioned antifreeze mechanism process is as follows: the entire refrigeration system is shut down, but the water pump continues to run. This water pump is connected to the inlet of the circulating liquid side of the plate heat exchanger, and the water pump continues to run until the exhaust pressure on the refrigerant side is equal to the return pressure on the refrigerant side.

[0057] In this embodiment, the plate heat exchanger can be protected from freezing through the above process. The power of the water pump can be adjusted according to the actual situation. Generally, the above-mentioned antifreeze mechanism should be implemented immediately.

[0058] Step S3: Further determine the relationship between the outlet water temperature e on the refrigerant side of the plate heat exchanger and the set refrigerant threshold g1. If the outlet water temperature e on the refrigerant side of the plate heat exchanger is greater than the set refrigerant threshold g1, proceed to step S4. If the outlet water temperature e on the refrigerant side of the plate heat exchanger is less than or equal to the set refrigerant threshold g1, further determine the relationship between the inlet water temperature f on the refrigerant side of the plate heat exchanger and the set refrigerant threshold g1. If the inlet water temperature f on the refrigerant side of the plate heat exchanger is less than or equal to the set refrigerant threshold g1, the antifreeze mechanism should be activated. If the inlet water temperature f on the refrigerant side of the plate heat exchanger is greater than the refrigerant threshold g1, continuous monitoring should be performed.

[0059] In step S3, specifically when the inlet water temperature f on the refrigerant side of the plate heat exchanger is greater than the set refrigerant threshold g1, the difference between the inlet water temperature f and the set refrigerant threshold can be further determined, and the relationship between this difference and the set warning temperature difference can be determined. If this difference is less than the warning temperature difference, it means that although the inlet water temperature f on the refrigerant side of the plate heat exchanger is greater than the refrigerant threshold g1, the outlet water temperature e on the refrigerant side of the plate heat exchanger is also less than the set refrigerant threshold g1 in this case. In addition, the inlet water temperature f on the refrigerant side of the plate heat exchanger is still within the warning temperature difference range above the critical value. Therefore, the collection and comparison of temperature and pressure data should be accelerated, and the process should return to S2 based on the temperature data.

[0060] In this embodiment, when the outlet water temperature on the refrigerant side is less than g1 and the inlet water temperature on the refrigerant side is greater than g1, since the specific value of the inlet water temperature on the refrigerant side exceeding g1 is not clear in a short time, it is necessary to make a further judgment based on the warning temperature difference.

[0061] Based on the above judgment, if the difference between the inlet water temperature f and the refrigerant threshold g1 is greater than the above warning temperature difference, then there is no need to accelerate the collection and comparison process. Instead, the process returns directly to step S1 and performs detection and subsequent judgment according to the original collection cycle.

[0062] In this embodiment, if the difference is outside the warning temperature difference, no additional acceleration processing is required.

[0063] Step S4: After completing step S3, further determine the relationship between the inlet water temperature on the refrigerant side of the plate heat exchanger and the set refrigerant threshold g1. If the inlet water temperature on the refrigerant side of the plate heat exchanger is greater than the set refrigerant threshold g1, the entire control judgment process can be terminated. If the inlet water temperature on the refrigerant side of the plate heat exchanger is less than or equal to the set refrigerant threshold g1, an alarm judgment process will be initiated immediately.

[0064] The aforementioned warning judgment process mainly includes the following steps: Calculate the instantaneous outlet water temperature on the refrigerant side and the inlet water temperature on the refrigerant side of the plate heat exchanger, and calculate the difference between the two to obtain the first difference value. At the same time, set the maximum value of the antifreeze temperature difference. The set antifreeze temperature difference has a standard range, and the maximum value is taken here. Determine the relationship between the first difference value and the maximum value of the antifreeze temperature difference. If the first difference value is greater than the maximum value of the antifreeze temperature difference, the electronic expansion valve should be adjusted. This electronic expansion valve is connected to the refrigerant side inlet of the plate heat exchanger. If the first difference value is less than or equal to the maximum value of the antifreeze temperature difference, the antifreeze mechanism will be activated after a set interval.

[0065] Unlike Example 1, in step S4 of this example, historical time period data is specifically used for further judgment.

[0066] In step S4, if the inlet water temperature f on the refrigerant side of the plate heat exchanger is greater than the set refrigerant threshold g1, it is initially determined that a normal shutdown will be performed. In this embodiment, historical time period data is used for further judgment.

[0067] The specific process is as follows: a historical time period database is established under the judgment logic condition. Based on the determined historical time period, the corresponding historical time period data is retrieved. The historical time period data includes the inlet water temperature f or outlet water temperature e of the refrigerant side within the historical time period. The cases where the inlet water temperature f or outlet water temperature e of the refrigerant side in the historical time period data does not meet the condition of being greater than g1 are counted. Based on the time difference between the historical time period and the current time period, it is determined whether to switch to the warning judgment process.

[0068] The decision to proceed to the alert judgment process is based on the time difference between historical time periods and the current time period. In this embodiment, a specific implementation process is also proposed: First, a mapping model is established between the time difference between historical time periods and the current time period and the judgment accuracy of the current time period. In this mapping model, each time difference corresponds to a judgment accuracy range for a time period. Finally, the current time period judgment is determined based on the calculated time difference to determine whether the judgment of the current time period is within the standard range of time period judgment accuracy.

[0069] In this embodiment, the accuracy standard range shell for time period judgment within the mapping model is fine-tuned according to the actual situation.

[0070] Example 3 Based on Embodiment 1 or Embodiment 2 above, this embodiment proposes a specific scenario for the application of an automatic control method for antifreeze of a chiller plate heat exchanger, referring to... Figure 1 The system includes a plate heat exchanger 1, wherein the plate heat exchanger 1 includes an inlet f and an outlet e on the refrigerant side, and an inlet a and an outlet c on the circulating liquid side. Temperature sensors are installed at the inlet f and outlet e on the refrigerant side and at the inlet a and outlet c on the circulating liquid side of the plate heat exchanger 1.

[0071] The inlet a of the circulating liquid side of the plate heat exchanger 1 is connected to a water pump. The other end of the water pump is connected to a level switch 6. The other end of the level switch 6 is connected to a return water temperature sensor 5 and a drain outlet 8. The other end of the return water temperature sensor 5 is connected to a customer heat source 7. The other end of the customer heat source 7 is connected to a water pressure sensor 4 and an outlet water temperature sensor 3 in sequence. The outlet water temperature sensor 3 can collect the temperature of the outlet c. Alternatively, a temperature sensor can be set at the end near the outlet c.

[0072] The refrigerant inlet f of the plate heat exchanger 1 is connected to the second electronic expansion valve 11. The other end of the second electronic expansion valve 11 is connected to the dryer filter 9. The other end of the dryer filter 9 is connected to the condenser 19. The other end of the condenser 19 is connected in sequence to the first pressure sensor 12 and the exhaust temperature sensor 13. The other end of the exhaust temperature sensor 13 is connected to the compressor 16. The other end of the compressor 16 is connected to the return gas temperature sensor 15. The other end of the return gas temperature sensor 15 is connected to the second pressure sensor 14. The second pressure sensor 14 is connected to the refrigerant outlet e of the plate heat exchanger 1.

[0073] In this embodiment, the first pressure sensor 12 and the second pressure sensor 14 are the exhaust and return pressures of the refrigerant described in Embodiment 1 or 2. The electronic expansion valve described in Embodiment 1 or 2 is the second electronic expansion valve 11.

[0074] The first pressure sensor 12 is also connected to the inlet f on the refrigerant side of the plate heat exchanger 1 via the first electronic expansion valve 10.

Claims

1. An automatic control method for antifreeze protection of a plate heat exchanger in a chiller, characterized in that, Includes the following steps: S1, acquire the refrigerant side and circulating liquid side temperature data of the plate heat exchanger, and the exhaust and return pressure of the refrigerant; S2, determine whether the outlet water temperature on the circulating fluid side is less than or equal to the circulating fluid threshold d. If yes, run the antifreeze mechanism; otherwise, perform a normal shutdown and proceed to S3. S3, determine whether the outlet water temperature on the refrigerant side is greater than the refrigerant threshold g1. If yes, proceed to S4; if no, determine whether the inlet water temperature on the refrigerant side is less than or equal to g1. If yes, run the antifreeze mechanism; if no, continue monitoring. S4, determine if the inlet water temperature on the refrigerant side is greater than g1; if yes, end the process; otherwise, issue a warning.

2. The automatic control method for antifreeze of a plate heat exchanger in a chiller according to claim 1, characterized in that, The antifreeze mechanism is specifically as follows: The entire refrigeration system shuts down, but the water pump connected to the circulating liquid inlet of the plate heat exchanger continues to run until the refrigerant discharge pressure equals the refrigerant return pressure.

3. The automatic control method for antifreeze of a plate heat exchanger in a chiller according to claim 1 or 2, characterized in that, The warning judgment specifically includes: Calculate the difference between the outlet water temperature and the inlet water temperature on the refrigerant side at real time to obtain the first difference value, and set the maximum antifreeze temperature difference value. Determine whether the first difference value is greater than the maximum antifreeze temperature difference value. If it is, adjust the electronic expansion valve connected to the refrigerant side inlet of the plate heat exchanger. If not, run the antifreeze mechanism after a set interval.

4. An automatic control method for antifreeze of a plate heat exchanger in a chiller according to claim 1 or 2, characterized in that, In step S3, when the inlet water temperature on the refrigerant side is greater than g1, the difference between the inlet water temperature on the refrigerant side and g1 is determined. If the difference is less than the warning temperature difference, the collection and comparison of temperature and pressure data are accelerated, and the process is returned to S2 based on the temperature data.

5. The automatic control method for antifreeze of a plate heat exchanger in a chiller according to claim 4, characterized in that, If the difference between the inlet water temperature on the refrigerant side and g1 is greater than the warning temperature difference, then return directly to step S1 and perform the detection according to the original collection cycle.

6. An automatic control method for antifreeze of a plate heat exchanger in a chiller according to claim 1, 2, or 5, characterized in that, In step S4, if the inlet water temperature on the refrigerant side is greater than g1, it is initially determined that a normal shutdown will be performed. Further judgment will be made through a future set cycle: the inlet water temperature and outlet water temperature on the refrigerant side within the future set cycle will be continuously judged against g1 to determine whether there is a situation where the inlet water temperature or outlet water temperature on the refrigerant side does not meet the condition of being greater than g1 within the future set cycle. If so, it is also necessary to switch to the warning judgment process.

7. An automatic control method for antifreeze protection of a plate heat exchanger in a chiller according to claim 1, 2, or 5, characterized in that, In step S4, if the inlet water temperature on the refrigerant side is greater than g1, it is initially determined that a normal shutdown will be performed. Further judgment is made using historical time period data: a historical time period database is created for this condition, the corresponding historical time period data is retrieved according to the determined historical time period, the cases in which the inlet water temperature or outlet water temperature on the refrigerant side in the historical time period data does not meet the condition of being greater than g1 are statistically analyzed, and whether to switch to the warning judgment process is determined based on the time difference between the historical time period and the current time period.

8. The automatic control method for antifreeze of a plate heat exchanger in a chiller according to claim 7, characterized in that, The process of determining whether to enter the alert judgment process based on the time difference between the historical time period and the current time period specifically includes: creating a mapping model between the time difference between the historical time period and the current time period and the judgment accuracy of the current time period. Each time difference corresponds to a judgment accuracy range for a time period. The judgment of the current time period is determined based on the time difference to see if it is within the judgment accuracy standard range for the time period.

9. An automatic control method for antifreeze of a plate heat exchanger in a chiller according to claim 1 or 2, characterized in that, The temperature data of the refrigerant side and the circulating liquid side of the plate heat exchanger are obtained through temperature acquisition devices on the refrigerant side and the circulating liquid side; the exhaust and return pressures of the refrigerant are obtained through pressure acquisition devices.

10. An automatic control system for antifreeze of a plate heat exchanger in a chiller, applicable to the automatic control method for antifreeze of a plate heat exchanger in a chiller as described in any one of claims 1-9, characterized in that, The system includes a central control center for recording process data and sending commands. The central control center is connected to a data acquisition module, which can acquire data from temperature and pressure acquisition devices. The data acquisition module is also connected to a temperature judgment module, which is connected to a mechanism selection module.

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