Evaporative cooling type magnetic levitation oil-free variable frequency centrifugal refrigeration unit

Abstract

The present application relates to the technical field of refrigeration equipment, and more particularly to an evaporative cold magnetic suspension oil-free variable frequency centrifugal refrigeration unit, comprising a full-liquid falling film evaporator, a magnetic suspension compressor, an evaporative condenser, a liquid accumulator, a supercooler, a frequency conversion cabinet and a pressure balance pipeline, the gas phase outlet of the full-liquid falling film evaporator is communicated with the gas suction end of the magnetic suspension compressor, the exhaust end of the magnetic suspension compressor is communicated with the evaporative condenser through an exhaust pipeline and a one-way valve, the evaporative condenser supplies liquid to the full-liquid falling film evaporator through the liquid accumulator, a high-pressure liquid throttling valve, the supercooler and a medium-pressure liquid throttling valve, a liquid collecting bag is arranged at the bottom of the liquid accumulator, the liquid collecting bag supplies liquid to the cooling branch of the frequency conversion cabinet and the cooling branch of the magnetic suspension compressor, and the cooling return liquid returns to the gas phase area of the full-liquid falling film evaporator, and the pressure balance pipeline with an electric valve arranged between the liquid accumulator and the gas phase area of the full-liquid falling film evaporator can improve the refrigeration efficiency of low-temperature refrigerant, and reduce the risks of liquid carrying, surge and overheating of the frequency conversion cabinet.

Description

Technical Field

[0001] This invention relates to the field of refrigeration equipment technology, and in particular to an evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller unit. Background Technology

[0002] Magnetic levitation oil-free variable frequency centrifugal chiller units utilize magnetic levitation bearings to support high-speed centrifugal impellers, which can reduce friction losses, oil return management, and oil film thermal resistance problems caused by traditional oil-lubricated bearings. They are suitable for producing high-efficiency chilled water or low-temperature refrigerants. For low-temperature refrigeration systems using ethylene glycol solution, glacial refrigerant, calcium chloride aqueous solution, sodium chloride aqueous solution, or heat transfer oil as refrigerants, the unit not only needs a stable evaporation heat exchange and compression process, but also needs to solve the problems of evaporative cooling and condensation, low-temperature liquid supply, cooling of internal heat-generating components of the magnetic levitation compressor, heat dissipation of the inverter cabinet, and pressure balance after shutdown. Therefore, evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller units are needed.

[0003] Existing magnetic levitation chiller units typically employ a refrigeration cycle consisting of a flooded evaporator, condenser, throttling device, and magnetic levitation compressor. Load adaptation is achieved through compressor frequency conversion regulation. A search revealed a patent with publication number CN103175276A, which discloses an air-cooled DC inverter magnetic levitation natural cold source chiller unit. This solution uses a magnetic levitation compressor, air-cooled condenser, throttling valve, and evaporator to form a refrigeration loop, combined with a natural cold source circulating water system to achieve energy-saving operation. Another patent, publication number CN110455002A, discloses a motor cooling system for a magnetic levitation centrifugal chiller unit, focusing on cooling the stator and rotor of the magnetic levitation centrifugal compressor motor. While these solutions demonstrate the technical concepts of oil-free operation of the magnetic levitation compressor and air cooling or motor cooling, they do not provide an integrated structural design for the evaporative condenser, low-temperature refrigerant refrigeration, stable liquid supply during the start-up phase of the liquid receiver, refrigerant cooling of the frequency converter cabinet, and pressure balance during shutdown.

[0004] In actual operation, if only a conventional condenser and ordinary liquid supply structure are used, the refrigerant liquid in the receiver may not be fully replenished during the initial startup of the unit, which may result in insufficient liquid supply. At the same time, the inverter and electrical components inside the inverter cabinet generate a lot of heat. If only ordinary air cooling is used, local overheating is likely to occur in high-temperature environments or high-load operation. The magnetic levitation compressor's internal components such as the magnetic levitation bearing and permanent magnet synchronous motor coil also require stable cooling. On the other hand, when the magnetic levitation compressor stops, the pressure on the evaporative condenser and receiver side is usually higher than the pressure on the full-liquid falling film evaporator side. If the pressure difference on both sides of the check valve is too large when restarting, it may affect the smooth discharge and induce surge. The high and low pressure difference may also cause refrigerant liquid to migrate into the evaporator, resulting in an excessively high evaporator liquid level, increasing the risk of liquid carryover in the compressor suction and liquid slugging in the impeller. Therefore, an evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller unit that can integrate evaporative cooling and condensation, subcooling gas replenishment, inverter cabinet cooling, compressor cooling, and pressure balancing is needed.

[0005] In light of this, in-depth research into the aforementioned issues led to the creation of this case. Summary of the Invention

[0006] The purpose of this invention is to provide an evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller unit to solve the problems of friction loss, oil return management, and oil film thermal resistance caused by existing oil-lubricated bearings mentioned in the background art. It is suitable for the preparation of high-efficiency chilled water or low-temperature refrigerant. For low-temperature refrigeration systems using ethylene glycol solution, glacial refrigerant, calcium chloride aqueous solution, sodium chloride aqueous solution, or heat transfer oil as refrigerant, the unit not only needs a stable evaporative heat exchange and compression process, but also needs to solve the problems of evaporative cooling and condensation, low-temperature liquid supply, cooling of internal heat-generating components of the magnetic levitation compressor, heat dissipation of the inverter cabinet, and pressure balance after shutdown.

[0007] To achieve the above objectives, the present invention provides the following technical solution: an evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller unit, including a flooded falling film evaporator.

[0008] The vapor phase outlet of the flooded falling film evaporator is connected to the suction end of the magnetic levitation compressor. The discharge end of the magnetic levitation compressor is connected to an evaporative condenser. A liquid receiver is connected to one side of the evaporative condenser. A subcooler is provided at one end of the liquid receiver.

[0009] The magnetic levitation compressor has an exhaust pipe connected to its exhaust end. One end of the exhaust pipe is connected to a one-way valve, and one end of the one-way valve is connected to an evaporative condenser. One end of the evaporative condenser is connected to an evaporative cold liquid outlet pipe, and one end of the evaporative cold liquid outlet pipe is connected to a liquid receiver. One end of the liquid receiver is connected to a high-pressure liquid outlet pipe, and one end of the high-pressure liquid outlet pipe is connected to a first dryer filter. One end of the first dryer filter is connected to a high-pressure liquid throttling valve, and one end of the high-pressure liquid throttling valve is connected to a subcooler. One end of the subcooler is connected to a subcooled liquid outlet pipe, and one end of the subcooled liquid outlet pipe is connected to a medium-pressure liquid throttling valve. One end of the medium-pressure liquid throttling valve is connected to a full-fill falling film evaporator.

[0010] Preferably, a temperature sensor is installed on the pipeline connected to the flooded falling film evaporator, a liquid level sensor is installed on the inner side of the flooded falling film evaporator, a refrigerant inlet temperature sensor is installed at the refrigerant inlet end of the flooded falling film evaporator, and a refrigerant outlet temperature sensor is installed at the refrigerant outlet end of the flooded falling film evaporator.

[0011] Preferably, the intake end of the magnetic levitation compressor is equipped with an intake temperature sensor and an intake pressure sensor, and the exhaust end of the magnetic levitation compressor is equipped with an exhaust pressure sensor and an exhaust temperature sensor.

[0012] Preferably, a medium-pressure connecting pipe is connected to one side of the subcooler, one end of the medium-pressure connecting pipe is connected to the medium-pressure air inlet of the magnetic levitation compressor, and a medium-pressure solenoid valve is connected to the outside of the medium-pressure connecting pipe.

[0013] Preferably, an evaporative cooling heat exchange coil is provided on the inner side of the evaporative condenser, an evaporative cooling heat dissipation fan is provided above the evaporative condenser, an evaporative cooling liquid equalization packing is provided below the evaporative cooling heat exchange coil, and an evaporative cooling water collection tank is provided at the bottom of the evaporative condenser.

[0014] Preferably, an evaporative cold spray pump is connected to one side of the evaporative cold water collection tank, an evaporative cold spray water pipe is connected to one end of the evaporative cold spray water pipe, an evaporative cold spray water equalization pipe is connected to one end of the evaporative cold water collection tank, a spray water temperature sensor is provided on one side of the evaporative cold water collection tank, and an electric heating tube is provided on the inner side of the evaporative cold water collection tank.

[0015] Preferably, the bottom of the liquid storage tank is provided with a liquid collection bag, one side of the liquid collection bag is connected to a first cooling liquid outlet pipe, one end of the first cooling liquid outlet pipe is connected to a second drying filter, one end of the second drying filter is connected to the cooling inlet of the frequency converter cabinet, one end of the frequency converter cabinet is connected to a first cooling liquid return pipe, and the first cooling liquid return pipe is connected to the gas phase zone of the full-liquid falling film evaporator.

[0016] Preferably, the inside of the frequency converter cabinet is provided with a frequency converter, a finned heat exchanger and a fan. A first solenoid valve is provided in the cooling branch where the frequency converter is located, and a second solenoid valve is provided in the cooling branch where the finned heat exchanger and the fan are located. A frequency converter cabinet temperature sensor is provided on one side of the frequency converter cabinet, and a frequency converter built-in temperature sensor is provided on one side of the frequency converter.

[0017] Preferably, a second cooling liquid outlet pipe is connected to one side of the liquid collection bag, a third drying filter is connected to one end of the second cooling liquid outlet pipe, a third solenoid valve is connected to one end of the third drying filter, one end of the third solenoid valve is connected to the cooling liquid inlet of the magnetic levitation compressor, and a second cooling liquid return pipe is connected to the cooling liquid return outlet of the magnetic levitation compressor. The second cooling liquid return pipe is connected to the gas phase zone of the full-fill falling film evaporator.

[0018] Preferably, a pressure balancing pipeline is connected between the liquid receiver and the gas phase zone of the full-liquid falling film evaporator. An electric valve is connected to the outside of the pressure balancing pipeline. The electric valve is used to open the pressure balancing pipeline after the magnetic levitation compressor stops running, so that the pressure between the liquid receiver and the full-liquid falling film evaporator tends to be balanced.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. This evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller unit forms a low-temperature refrigerant refrigeration cycle through a flooded falling film evaporator, a magnetic levitation compressor, an evaporative condenser, a receiver, a subcooler, a high-pressure liquid throttling valve, a medium-pressure liquid throttling valve, and a medium-pressure gas injection pipeline. The refrigerant is cooled by the low-temperature, low-pressure refrigerant in the flooded falling film evaporator. The magnetic levitation compressor compresses the superheated low-temperature, low-pressure refrigerant gas into a high-temperature, high-pressure gas. The evaporative condenser completes condensation by absorbing heat through spray water evaporation and by forced ventilation through a cooling fan. Compared with a simple air-cooled condenser structure, this improves condensation efficiency and reduces condensation pressure and exhaust temperature. The subcooler, in conjunction with the medium-pressure connecting pipe and the medium-pressure solenoid valve, allows part of the medium-pressure refrigerant gas to enter the compressor's medium-pressure gas injection port, while another part of the medium-temperature, medium-pressure refrigerant subcooled liquid continues to flow into the evaporator through throttling, which improves operating efficiency and refrigeration stability under low-temperature conditions.

[0021] 2. This evaporative cooling type magnetic levitation oil-free variable frequency centrifugal chiller unit, by setting a liquid collection bag at the bottom of the liquid receiver and supplying liquid to the cooling branches of the frequency converter cabinet and the magnetic levitation compressor respectively, can provide a stable and usable refrigerant liquid during the unit start-up phase when the liquid receiver has not been fully replenished, avoiding short-term insufficient liquid supply in the cooling branches. The branch where the frequency converter is located and the branch where the finned heat exchanger and fan are located are controlled by the first solenoid valve and the second solenoid valve respectively. The liquid can be supplied as needed according to the detection results of the temperature sensor of the frequency converter cabinet and the temperature sensor built into the frequency converter, so as to keep the temperature of the frequency converter and the electrical components inside the cabinet within a reasonable range. The cooling branch of the magnetic levitation compressor supplies cooling to heat-generating components such as the magnetic levitation bearing and the permanent magnet synchronous motor coil through the second cooling liquid outlet pipe, the third drying filter and the third solenoid valve, reducing the internal heat load of the compressor and improving the operational reliability of the magnetic levitation compressor.

[0022] 3. This evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller unit, by installing a pressure balancing pipeline and electric valve between the liquid receiver and the vapor phase zone of the flooded falling film evaporator, can actively balance the pressure between the liquid receiver and the evaporator after the magnetic levitation compressor stops. This prevents refrigerant liquid from migrating to the low-pressure evaporator due to long-term high-pressure side pressure, thereby reducing the risk of excessively high evaporator liquid level and liquid carryover during restart. Simultaneously, the reduced pressure difference across the one-way valve during restart after pressure balancing facilitates smooth compressor exhaust through the one-way valve into the evaporative condenser, reducing surge and backflush risks. This gives the unit higher start-up and shutdown safety and operational stability in low-temperature process cooling scenarios. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the system flow structure of the present invention.

[0024] In the diagram: 1. Flooded falling film evaporator; 2. Temperature sensor; 3. Magnetic levitation compressor; 4. Exhaust pipe; 5. One-way valve; 6. Evaporative condenser; 7. Evaporative cold liquid outlet pipe; 8. Liquid receiver; 9. High-pressure liquid outlet pipe; 10. First dryer filter; 11. High-pressure liquid throttling valve; 12. Subcooler; 13. Subcooled liquid outlet pipe; 14. Medium-pressure liquid throttling valve; 15. First cooling liquid outlet pipe; 16. Second dryer filter; 17. Frequency converter cabinet; 18. First solenoid valve; 19. Second solenoid valve; 20. First cooling liquid return pipe; 21. Second cooling liquid outlet pipe; 22. Third dryer filter; 23. Third solenoid valve; 24. Second cooling liquid return pipe; 25. Medium-pressure connecting pipe; 26. Medium-pressure... 27. Solenoid valve; 28. Liquid level sensor; 29. ​​Refrigerant inlet temperature sensor; 30. Refrigerant outlet temperature sensor; 31. Suction temperature sensor; 32. Suction pressure sensor; 33. Exhaust pressure sensor; 34. Exhaust temperature sensor; 35. Evaporative cooling heat exchange coil; 36. Evaporative cooling heat dissipation fan; 37. Evaporative cooling liquid equalization packing; 38. Evaporative cooling water collection tank; 39. Evaporative cooling spray pump; 40. Evaporative cooling spray water pipe; 41. Evaporative cooling spray water equalization pipe; 42. Spray water temperature sensor; 43. Electric heating tube; 44. Liquid collection bag; 45. Variable frequency cabinet temperature sensor; 46. Variable frequency drive built-in temperature sensor; 47. Variable frequency drive; 48. Finned heat exchanger and fan; 49. Electric valve; 40. Pressure balancing pipeline. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Please see Figure 1 This invention provides a technical solution: an evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller unit, including a flooded falling film evaporator 1.

[0027] The vapor phase outlet of the full-liquid falling film evaporator 1 is connected to the suction end of the magnetic levitation compressor 3. The discharge end of the magnetic levitation compressor 3 is connected to the evaporative condenser 6. A liquid receiver 8 is connected to one side of the evaporative condenser 6. A subcooler 12 is provided at one end of the liquid receiver 8.

[0028] The exhaust end of the magnetic levitation compressor 3 is connected to an exhaust pipe 4. One end of the exhaust pipe 4 is connected to a one-way valve 5. One end of the one-way valve 5 is connected to an evaporative condenser 6. One end of the evaporative condenser 6 is connected to an evaporative cold liquid outlet pipe 7. One end of the evaporative cold liquid outlet pipe 7 is connected to a liquid receiver 8. One end of the liquid receiver 8 is connected to a high-pressure liquid outlet pipe 9. One end of the high-pressure liquid outlet pipe 9 is connected to a first dryer filter 10. One end of the first dryer filter 10 is connected to a high-pressure liquid throttling valve 11. One end of the high-pressure liquid throttling valve 11 is connected to a subcooler 12. One end of the subcooler 12 is connected to a subcooled liquid outlet pipe 13. One end of the subcooled liquid outlet pipe 13 is connected to a medium-pressure liquid throttling valve 14. One end of the medium-pressure liquid throttling valve 14 is connected to a full-fill falling film evaporator 1.

[0029] Furthermore, a temperature sensor 2 is installed on the pipeline connected to the flooded falling film evaporator 1, a liquid level sensor 27 is installed inside the flooded falling film evaporator 1, a refrigerant inlet temperature sensor 28 is installed at the refrigerant inlet end of the flooded falling film evaporator 1, and a refrigerant outlet temperature sensor 29 is installed at the refrigerant outlet end of the flooded falling film evaporator 1. Through the installation of the refrigerant inlet temperature sensor 28 and the refrigerant outlet temperature sensor 29, the control system can acquire the temperature change of the refrigerant before and after entering the flooded falling film evaporator 1, in ethylene glycol... In low-temperature refrigeration conditions where the solution is used as the refrigerant, the refrigeration demand can be determined based on the refrigerant outlet temperature as the main control value. When the outlet temperature is higher than the target temperature, the unit is started and the operating frequency of the magnetic levitation compressor 3 is increased or the opening of the throttle valve is increased. When the outlet temperature is lower than the target temperature, the unit is controlled to reduce the load or stop, thereby keeping the low-temperature refrigerant temperature stable. Through the setting of the liquid level sensor 27, the refrigerant level in the full-liquid falling film evaporator 1 can be monitored in real time, avoiding insufficient heat exchange due to the evaporator liquid level being too low, and also avoiding the risk of liquid carryover during suction due to the liquid level being too high.

[0030] Furthermore, the magnetic levitation compressor 3 is equipped with an intake temperature sensor 30 and an intake pressure sensor 31 at its intake end, and an exhaust pressure sensor 32 and an exhaust temperature sensor 33 at its exhaust end. The intake temperature sensor 30 and the intake pressure sensor 31 enable the control system to determine the overheating state of the magnetic levitation compressor 3's intake and the low-pressure side operating state, thus preventing the compressor from drawing in liquid refrigerant. The exhaust pressure sensor 32 and the exhaust temperature sensor 33 allow for real-time feedback of the high pressure and high temperature at the exhaust end. When the exhaust pressure increases, the control system can adjust the operating state of the evaporative cooling fan 35 and the evaporative cooling spray pump 38 in conjunction. When the exhaust temperature rises abnormally, the control system can control the magnetic levitation compressor 3 to reduce load or shut down for protection, thereby improving the operational safety of the magnetic levitation compressor 3 under low-temperature refrigeration conditions.

[0031] Furthermore, a medium-pressure connecting pipe 25 is connected to one side of the subcooler 12. One end of the medium-pressure connecting pipe 25 is connected to the medium-pressure gas injection port of the magnetic levitation compressor 3. A medium-pressure solenoid valve 26 is connected to the outside of the medium-pressure connecting pipe 25. Through the setting of the subcooler 12 and the medium-pressure connecting pipe 25, the high-pressure liquid refrigerant can form a medium-pressure gas-liquid separation heat exchange process in the subcooler 12 after throttling. The medium-pressure gas generated therein enters the medium-pressure gas injection port of the magnetic levitation compressor 3 through the medium-pressure connecting pipe 25, which can improve the intermediate gas injection efficiency during the compression process and reduce the compressor discharge temperature. Through the setting of the medium-pressure solenoid valve 26, the medium-pressure gas injection passage can be controlled to open and close according to the unit load, discharge temperature and compressor operating status. When the demand for ethylene glycol cooling is large at high load or low temperature, the gas injection is enhanced. When the operation is low load, the gas injection is closed or reduced, thereby improving the overall energy efficiency and operational stability of the unit.

[0032] Furthermore, an evaporative cooling heat exchange coil 34 is installed inside the evaporative condenser 6, an evaporative cooling heat dissipation fan 35 is installed above the evaporative condenser 6, an evaporative cooling liquid equalization packing 36 is installed below the evaporative cooling heat exchange coil 34, and an evaporative cooling water collection tank 37 is installed at the bottom of the evaporative condenser 6. Through the arrangement of the evaporative cooling heat exchange coil 34, the high-temperature and high-pressure refrigerant gas discharged from the magnetic levitation compressor 3 can be condensed and heat exchanged inside the coil. Through the arrangement of the evaporative cooling heat dissipation fan 35 and the evaporative cooling liquid equalization packing 36, the sprayed water can be evenly distributed on the outer wall of the heat exchange coil and fully exchange heat with the outside air. The evaporation of water carries away the condensation heat, improving the condensation efficiency. Through the arrangement of the evaporative cooling water collection tank 37, the sprayed water after heat exchange can be recycled and reused, reducing cooling water consumption and enabling the evaporative condenser 6 to maintain a low condensation pressure in the high-temperature environment of summer.

[0033] Furthermore, an evaporative cooling spray pump 38 is connected to one side of the evaporative cooling water collection tank 37. One end of the evaporative cooling spray pump 38 is connected to an evaporative cooling spray water pipe 39, and one end of the evaporative cooling spray water pipe 39 is connected to an evaporative cooling spray water equalization pipe 40. A spray water temperature sensor 41 is installed on one side of the evaporative cooling water collection tank 37, and an electric heating tube 42 is installed inside the evaporative cooling water collection tank 37. Through the arrangement of the evaporative cooling spray pump 38, the evaporative cooling spray water pipe 39, and the evaporative cooling spray water equalization pipe 40, the spray water can... The water is evenly transported to the outside of the evaporative cooling heat exchange coil 34, improving the uniformity of wetting on the coil surface and avoiding insufficient heat exchange caused by local dry spots. The spray water temperature sensor 41 enables the control system to judge the changes in spray water temperature and adjust the operation of the spray pump and cooling fan in conjunction with the exhaust pressure sensor 32. The electric heating tube 42 prevents the spray water in the evaporative cooling water collection tank 37 from freezing in low-temperature environments, ensuring that the evaporative condenser 6 can still start and circulate spray reliably in winter or low-temperature environments.

[0034] Furthermore, a liquid collection bag 43 is provided at the bottom of the liquid storage tank 8. A first cooling liquid outlet pipe 15 is connected to one side of the liquid collection bag 43. A second drying filter 16 is connected to one end of the first cooling liquid outlet pipe 15. One end of the second drying filter 16 is connected to the cooling inlet of the frequency converter cabinet 17. A first cooling liquid return pipe 20 is connected to one end of the frequency converter cabinet 17. The first cooling liquid return pipe 20 is connected to the gas phase zone of the full-liquid falling film evaporator 1. Through the setting of the liquid collection bag 43, a certain amount of usable liquid is maintained at the bottom of the liquid storage tank 8. Even during the initial startup of the unit or when the liquid level in the receiver 8 fluctuates, the refrigerant can preferentially provide a stable source of coolant to the cooling branch of the inverter cabinet 17. Through the setting of the first cooling liquid outlet pipe 15 and the second dryer filter 16, the refrigerant before entering the inverter cabinet 17 is filtered and dried, reducing the blockage of the cooling branch by impurities and moisture. Through the setting of the first cooling liquid return pipe 20, the refrigerant after absorbing heat from the inverter cabinet 17 returns to the gas phase zone of the full-liquid falling film evaporator 1 to participate in the circulation, avoiding the accumulation of heat inside the inverter cabinet 17.

[0035] Furthermore, the inside of the frequency converter cabinet 17 is equipped with a frequency converter 46, a finned heat exchanger, and a fan 47. A first solenoid valve 18 is installed in the cooling branch where the frequency converter 46 is located, and a second solenoid valve 19 is installed in the cooling branch where the finned heat exchanger and fan 47 are located. A frequency converter cabinet temperature sensor 44 is installed on one side of the frequency converter cabinet 17, and a built-in frequency converter temperature sensor 45 is installed on one side of the frequency converter 46. Through the installation of the frequency converter cabinet temperature sensor 44, the second solenoid valve 19, and the finned heat exchanger and fan 47, the control system can detect the air temperature inside the cabinet. When the temperature exceeds the set value, the second solenoid valve 19 can be opened to allow refrigerant to enter the finned heat exchanger and fan 47, thereby cooling the air inside the frequency converter cabinet 17 as a whole. Through the configuration of the built-in temperature sensor 45 of the frequency converter, the first solenoid valve 18, and the cooling branch of the frequency converter 46, the first solenoid valve 18 can be opened directly when the temperature of the frequency converter 46 rises, thereby performing local enhanced cooling of the frequency converter 46. This forms a graded control mode of overall cooling of the air inside the cabinet and local cooling of the frequency converter, improving the temperature control reliability of the frequency converter cabinet 17 when operating under high load.

[0036] Furthermore, a second cooling liquid outlet pipe 21 is connected to one side of the liquid collection bag 43. One end of the second cooling liquid outlet pipe 21 is connected to a third dryer filter 22. One end of the third dryer filter 22 is connected to a third solenoid valve 23. One end of the third solenoid valve 23 is connected to the cooling liquid inlet of the magnetic levitation compressor 3. The cooling liquid return port of the magnetic levitation compressor 3 is connected to a second cooling liquid return pipe 24. The second cooling liquid return pipe 24 is connected to the vapor phase zone of the flooded falling film evaporator 1. Through the arrangement of the second cooling liquid outlet pipe 21 and the third solenoid valve 23, the liquid refrigerant in the liquid collection bag 43 can... The refrigerant can enter the compressor cooling channel according to the internal temperature requirements of the magnetic levitation compressor 3 to cool the internal heat-generating components of the compressor, such as the magnetic levitation bearing and the permanent magnet synchronous motor coil. The third dryer filter 22 intercepts the refrigerant impurities and moisture before entering the cooling branch of the magnetic levitation compressor 3, reducing the risk of cooling channel blockage. The second cooling return pipe 24 allows the heat-absorbing liquid refrigerant or gas-liquid mixed refrigerant to return to the gas phase region of the full-liquid falling film evaporator 1, avoiding the formation of liquid accumulation in the cooling branch and improving the thermal stability of the magnetic levitation compressor 3 during long-term operation.

[0037] Furthermore, a pressure balancing pipeline 49 is connected between the liquid receiver 8 and the vapor phase zone of the flooded falling film evaporator 1. An electric valve 48 is connected to the outside of the pressure balancing pipeline 49. The electric valve 48 is used to open the pressure balancing pipeline 49 after the magnetic levitation compressor 3 stops running, so that the pressure between the liquid receiver 8 and the flooded falling film evaporator 1 tends to be balanced. Through the setting of the pressure balancing pipeline 49 and the electric valve 48, the high-pressure gas in the liquid receiver 8 can enter the system under the delayed control of the control system after the unit stops. In the vapor phase zone of the flooded falling film evaporator 1, the pressure difference between the high and low pressure sides is gradually reduced. After the pressure is balanced, when the unit is restarted, the refrigerant gas in the exhaust pipe 4 can more smoothly push open the one-way valve 5 and enter the evaporative condenser 6, reducing the risk of exhaust obstruction, backflow, and surge. At the same time, it can reduce the possibility of refrigerant liquid migrating to the flooded falling film evaporator 1 under the action of pressure difference, avoiding excessively high evaporator liquid level, liquid carryover in compressor suction, and liquid slugging in the impeller, thus improving the safety of restarting the magnetic levitation compressor 3 after shutdown.

[0038] Example:

[0039] 1. Low-temperature ethylene glycol refrigerant refrigeration mode: Ethylene glycol solution is used as the refrigerant. The refrigerant enters the heat exchange tube through the refrigerant inlet of the flooded falling film evaporator 1. After exchanging heat with the low-pressure evaporating refrigerant outside the heat exchange tube, it flows out from the refrigerant outlet. The refrigerant inlet temperature sensor 28 and the refrigerant outlet temperature sensor 29 detect the temperature before and after cooling, respectively. The control system can select the outlet temperature as the control value. When the outlet temperature is higher than the target temperature, the unit starts and adjusts the frequency of the magnetic levitation compressor 3 and the opening of the throttle valve. When the outlet temperature is lower than the target temperature, the unit reduces the load or stops running.

[0040] 2. High-temperature cooling operation of the frequency converter cabinet: When the frequency converter cabinet temperature sensor 44 detects that the air temperature inside the cabinet is higher than the set value, the second solenoid valve 19 opens. The refrigerant enters the finned heat exchanger and fan 47 from the liquid collection bag 43 through the first cooling liquid outlet pipe 15 and the second dryer filter 16, absorbing the heat of the air inside the cabinet and partially vaporizing. When the built-in temperature sensor 45 of the frequency converter detects that the temperature of the frequency converter 46 is higher than the set value, the first solenoid valve 18 opens, and the refrigerant directly cools the frequency converter 46, thereby realizing the graded control of local cooling of the frequency converter and overall cooling of the air inside the cabinet.

[0041] 3. Pressure balance condition after shutdown: After the magnetic levitation compressor 3 stops running, the control system opens the electric valve 48 after a delay, allowing the high-pressure gas in the receiver 8 to enter the vapor phase region of the full-liquid falling film evaporator 1 through the pressure balance pipeline 49. After pressure balance, when the unit restarts, the refrigerant gas in the exhaust pipeline 4 can more smoothly push open the one-way valve 5 and enter the evaporative condenser 6, reducing the risk of surge and minimizing the migration of refrigerant liquid to the full-liquid falling film evaporator 1 under the influence of high and low pressure differences, which could cause the liquid level to be too high.

[0042] Working Principle: First, the refrigerant requiring cooling enters the heat exchange tubes inside the flooded falling film evaporator 1 through the refrigerant inlet, exchanging heat with the low-pressure evaporating refrigerant outside the tubes. After being cooled, the refrigerant flows out from the refrigerant outlet of the flooded falling film evaporator 1. The refrigerant inlet temperature sensor 28 measures the temperature of the refrigerant before cooling, and the refrigerant outlet temperature sensor 29 measures the temperature of the refrigerant after cooling. The control system selects either the inlet or outlet temperature as the start / stop control signal according to actual needs. When the measured temperature is higher than the set target value, the system starts; when the measured temperature is lower than the set target value, the system stops or operates with reduced load. The refrigerant outside the heat exchange tubes absorbs heat from the refrigerant and evaporates into a low-temperature, low-pressure superheated refrigerant gas. This low-temperature, low-pressure refrigeration... The superheated refrigerant gas enters the suction end of the magnetic levitation compressor 3 through the gas phase outlet of the flooded falling film evaporator 1. The magnetic levitation compressor 3 compresses it into high-temperature, high-pressure refrigerant superheated gas, which then enters the evaporative condenser 6 through the exhaust pipe 4 and the one-way valve 5. In the evaporative condenser 6, the high-temperature, high-pressure refrigerant gas flows within the evaporative cooling heat exchange coil 34. The evaporative cooling spray pump 38 sends water from the evaporative cooling water collection tank 37 through the evaporative cooling spray water pipe 39 into the evaporative cooling spray water equalization pipe 40. The evaporative cooling spray water equalization pipe 40 evenly sprays the spray water onto the outer wall of the evaporative cooling heat exchange coil 34. The spray water absorbs heat from the refrigerant in the coil and exchanges heat with the ambient air under the action of the evaporative cooling cooling fan 35. A portion of the spray water evaporates and absorbs heat, making the high-temperature, high-pressure refrigerant gas in the evaporative cooling heat exchange coil 34 evenly distributed. The high-temperature, high-pressure refrigerant superheated gas condenses into a high-temperature, high-pressure refrigerant liquid. Spray water falls into the evaporative cooling water collection tank 37 under gravity and is recycled. Simultaneously, the control system gradually turns the evaporative cooling fan 35 on or off based on the exhaust pressure value detected by the exhaust pressure sensor 32 to regulate the condensation pressure. The condensed high-temperature, high-pressure refrigerant liquid enters the liquid receiver 8 via the evaporative cooling liquid outlet pipe 7 for buffering. From the liquid receiver 8, it enters the first dryer filter 10 via the high-pressure liquid outlet pipe 9 to filter impurities and moisture. After being throttled and depressurized by the high-pressure liquid throttling valve 11, it enters the subcooler 12. In the subcooler 12, some refrigerant evaporates into a medium-pressure refrigerant gas due to the reduced pressure. This medium-pressure refrigerant gas enters the magnetic levitation compressor via the medium-pressure connecting pipe 25 and the medium-pressure solenoid valve 26. At the medium-pressure gas inlet of unit 3, another portion of the refrigerant forms a medium-temperature, medium-pressure subcooled liquid and enters the medium-pressure liquid throttling valve 14 through the cold liquid outlet pipe 13 for further throttling and pressure reduction. This forms a low-temperature, low-pressure refrigerant liquid, which then enters the submerged film evaporator 1 between the shell and heat exchange tubes to continue absorbing heat and evaporating, thus completing the main refrigeration cycle. During the main cycle operation, the liquid level sensor 27 monitors the refrigerant level in the submerged film evaporator 1 in real time. The control system compares the liquid level value with the target liquid level. When the liquid level is too low, the opening of the medium-pressure liquid throttling valve 14 is increased; when the liquid level is too high, the opening of the medium-pressure liquid throttling valve 14 is decreased, keeping the refrigerant level in the evaporator within a safe range. When the unit starts, the refrigerant liquid in the receiver 8 may not have been fully replenished by the evaporative condenser 6.The liquid collection bag 43, located at the bottom of the liquid receiver 8 and below the bottom of the cylinder, can maintain a certain amount of usable refrigerant liquid. A portion of the refrigerant liquid in the collection bag 43 enters the cooling branch of the frequency converter cabinet 17 via the first cooling outlet pipe 15 and the second dryer filter 16. It controls the cooling branch of the frequency converter 46 via the first solenoid valve 18 and the cooling branch of the finned heat exchanger and fan 47 via the second solenoid valve 19. After absorbing heat from the electrical components in the frequency converter 46 and the frequency converter cabinet 17, the refrigerant partially or completely vaporizes and returns to the vapor phase zone of the full-liquid falling film evaporator 1 via the first cooling return pipe 20. The control system uses the frequency converter cabinet temperature sensor 44 and the frequency converter's built-in temperature sensor 45 to determine the air temperature inside the cabinet and the frequency converter temperature, thereby controlling the opening and closing of the first solenoid valve 18 and the second solenoid valve 19. The remaining portion of the refrigerant liquid in the collection bag 43 flows through the second cooling outlet pipe 2... 1. The third dryer filter 22 and the third solenoid valve 23 enter the cooling inlet of the magnetic levitation compressor 3 to cool the internal heat-generating components such as the magnetic levitation bearing and the permanent magnet synchronous motor coil. The liquid or gas-liquid mixture after absorbing heat returns to the gas phase zone of the full-float falling film evaporator 1 through the second cooling return pipe 24. When the magnetic levitation compressor 3 stops running, the pressure in the evaporative condenser 6 and the liquid receiver 8 is higher than the pressure in the full-float falling film evaporator 1. The control system opens the electric valve 48, allowing the high-pressure refrigerant gas in the liquid receiver 8 to enter the gas phase zone of the full-float falling film evaporator 1 through the pressure balancing pipe 49 until the high and low pressure sides tend to be equal. This avoids the one-way valve 5 failing to open smoothly during restart, which could lead to exhaust backflow and compressor surge. It also reduces the risk of refrigerant liquid migrating to the full-float falling film evaporator 1 due to pressure difference, causing excessive liquid level, liquid carryover in compressor suction, and impeller liquid slugging.

[0043] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An evaporative cooling type magnetic levitation oil-free variable frequency centrifugal chiller unit, comprising a flooded falling film evaporator (1), characterized in that: The gas phase outlet of the full-liquid falling film evaporator (1) is connected to the suction end of the magnetic levitation compressor (3). The exhaust end of the magnetic levitation compressor (3) is connected to an evaporative condenser (6). A liquid receiver (8) is connected to one side of the evaporative condenser (6). A supercooler (12) is provided at one end of the liquid receiver (8). The exhaust end of the magnetic levitation compressor (3) is connected to an exhaust pipe (4). One end of the exhaust pipe (4) is connected to a one-way valve (5). One end of the one-way valve (5) is connected to an evaporative condenser (6). One end of the evaporative condenser (6) is connected to an evaporative cold liquid outlet pipe (7). One end of the evaporative cold liquid outlet pipe (7) is connected to a liquid receiver (8). One end of the liquid receiver (8) is connected to a high-pressure liquid outlet pipe (9). The high-pressure liquid outlet pipe (9)... One end is connected to a first drying filter (10), one end of the first drying filter (10) is connected to a high-pressure liquid throttle valve (11), one end of the high-pressure liquid throttle valve (11) is connected to a subcooler (12), one end of the subcooler (12) is connected to a subcooled liquid outlet pipeline (13), one end of the subcooled liquid outlet pipeline (13) is connected to a medium-pressure liquid throttle valve (14), and one end of the medium-pressure liquid throttle valve (14) is connected to a full-fill falling film evaporator (1).

2. The evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller unit according to claim 1, characterized in that: A temperature sensor (2) is installed on the pipeline connected to the full-liquid falling film evaporator (1), a liquid level sensor (27) is installed on the inner side of the full-liquid falling film evaporator (1), a refrigerant inlet temperature sensor (28) is installed at the refrigerant inlet end of the full-liquid falling film evaporator (1), and a refrigerant outlet temperature sensor (29) is installed at the refrigerant outlet end of the full-liquid falling film evaporator (1).

3. The evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller unit according to claim 1, characterized in that: The magnetic levitation compressor (3) is equipped with an intake temperature sensor (30) and an intake pressure sensor (31) at its intake end, and an exhaust pressure sensor (32) and an exhaust temperature sensor (33) at its exhaust end.

4. The evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller unit according to claim 1, characterized in that: One side of the subcooler (12) is connected to a medium-pressure connecting pipe (25), one end of which is connected to the medium-pressure air supply port of the magnetic levitation compressor (3), and a medium-pressure solenoid valve (26) is connected to the outside of the medium-pressure connecting pipe (25).

5. The evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller unit according to claim 1, characterized in that: An evaporative cooling heat exchange coil (34) is provided on the inner side of the evaporative condenser (6), an evaporative cooling heat dissipation fan (35) is provided above the evaporative condenser (6), an evaporative cooling liquid equalization packing (36) is provided below the evaporative cooling heat exchange coil (34), and an evaporative cooling water collection tank (37) is provided at the bottom of the evaporative condenser (6).

6. The evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller unit according to claim 5, characterized in that: An evaporative cold water collection tank (37) is connected to an evaporative cold spray pump (38) on one side, an evaporative cold spray water pipe (39) is connected to one end of the evaporative cold spray water pipe (39), an evaporative cold spray water equalization pipe (40) is connected to one end of the evaporative cold water collection tank (37), a spray water temperature sensor (41) is provided on one side of the evaporative cold water collection tank (37), and an electric heating tube (42) is provided on the inner side of the evaporative cold water collection tank (37).

7. The evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller unit according to claim 1, characterized in that: The bottom of the liquid storage tank (8) is provided with a liquid collection bag (43). One side of the liquid collection bag (43) is connected to a first cooling liquid outlet pipe (15). One end of the first cooling liquid outlet pipe (15) is connected to a second drying filter (16). One end of the second drying filter (16) is connected to the cooling inlet of the frequency converter cabinet (17). One end of the frequency converter cabinet (17) is connected to a first cooling liquid return pipe (20). The first cooling liquid return pipe (20) is connected to the gas phase zone of the full-liquid falling film evaporator (1).

8. The evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller unit according to claim 7, characterized in that: The inverter cabinet (17) is equipped with an inverter (46), a finned heat exchanger and a fan (47) on its inner side. The cooling branch where the inverter (46) is located is equipped with a first solenoid valve (18), and the cooling branch where the finned heat exchanger and the fan (47) are located is equipped with a second solenoid valve (19). The inverter cabinet temperature sensor (44) is installed on one side of the inverter cabinet (17), and the inverter (46) is equipped with a built-in inverter temperature sensor (45) on one side of the inverter.

9. The evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller unit according to claim 7, characterized in that: The liquid collection bag (43) is connected to a second cooling liquid outlet pipe (21) on one side. A third drying filter (22) is connected to one end of the second cooling liquid outlet pipe (21). A third solenoid valve (23) is connected to one end of the third drying filter (22). One end of the third solenoid valve (23) is connected to the cooling liquid inlet of the magnetic levitation compressor (3). A second cooling liquid return pipe (24) is connected to the cooling liquid return port of the magnetic levitation compressor (3). The second cooling liquid return pipe (24) is connected to the gas phase zone of the full-liquid falling film evaporator (1).

10. The evaporative cooling magnetic levitation oil-free variable frequency centrifugal chiller unit according to claim 1, characterized in that: A pressure balancing pipeline (49) is connected between the liquid receiver (8) and the gas phase zone of the full-liquid falling film evaporator (1). An electric valve (48) is connected to the outside of the pressure balancing pipeline (49). The electric valve (48) is used to open the pressure balancing pipeline (49) after the magnetic levitation compressor (3) stops running, so that the pressure between the liquid receiver (8) and the full-liquid falling film evaporator (1) tends to be balanced.

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