A magnetic levitation centrifugal chiller unit with tank pump liquid supply and its control method

Abstract

This invention relates to a magnetic levitation centrifugal chiller unit with a tank pump for liquid supply and its control method. A low-pressure circulating tank is installed in the chiller unit, along with working refrigerant pumps corresponding to the evaporators. The operating load of the magnetic levitation compressor is adjusted based on the relationship between the chiller unit's real-time suction pressure P and the target pressure setpoint P0, ensuring that the chiller unit's cooling capacity matches the user's load. When a mismatch between the chiller unit's cooling capacity and the user's load causes fluctuations in the liquid level within the low-pressure circulating tank, the operating load of the magnetic levitation compressor and the operating frequency of the working refrigerant pumps are coordinated and controlled to maintain a stable liquid level in the low-pressure circulating tank. Multi-level protection logic is provided for the low-pressure circulating tank's liquid level, which not only prevents frequent start-stop cycles of the magnetic levitation compressor due to frequent liquid level alarms, extending equipment life, but also prevents liquid slugging in the magnetic levitation compressor due to excessively high liquid levels and cavitation of the refrigerant pump due to excessively low liquid levels.

Description

Technical Field

[0001] This invention relates to a magnetic levitation centrifugal chiller unit with a tank pump for liquid supply and its control method, belonging to the technical field of magnetic levitation centrifugal chiller units. Background Technology

[0002] The barrel pump refrigeration system uses a refrigerant pump to force multiple refrigerant cycles, resulting in high heat exchange efficiency, large hydraulic head, and the ability to supply refrigerant to multiple evaporators simultaneously. It is widely used in large cold storage facilities, large air conditioning systems, food processing, and chemical production.

[0003] Currently, conventional screw or oil centrifugal chiller tank pump liquid supply systems contain refrigeration oil. Since the refrigeration oil in the low-pressure circulating tank is concentrated in the upper layer of the refrigerant, it fluctuates greatly with the refrigerant level. The oil return problem of the tank pump liquid supply system has always been a design challenge and key point. Inevitably, some refrigeration oil enters the evaporator terminal with the refrigerant pump, affecting heat transfer and refrigeration efficiency.

[0004] Meanwhile, magnetic levitation centrifugal refrigeration technology has made significant progress in recent years and has been widely applied in the field of chiller units. The core advantage of magnetic levitation centrifugal chiller units lies in the fact that their compressors use magnetic levitation bearing technology, which achieves contactless and oil-free suspension support of the rotor. This results in magnetic levitation centrifugal chiller units operating completely without oil, with extremely low friction loss, stable operation, low noise, and a wide adjustment range.

[0005] Therefore, there is an urgent need to innovatively combine tank pump liquid supply technology with oil-free magnetic levitation compression technology to meet the high-efficiency cooling needs of magnetic levitation centrifugal chillers in large-scale cooling scenarios. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a magnetic levitation centrifugal chiller unit with a drum pump-supply system and its control method. Combining the advantages of an oil-free magnetic levitation compressor and a drum pump-supply system, the chiller unit achieves a significantly higher energy efficiency ratio than traditional oil-containing drum pump refrigeration systems. Multi-level protection logic is provided for the low-pressure circulating tank liquid level, which not only prevents frequent start-stop cycles of the magnetic levitation refrigeration compressor due to frequent liquid level alarms, thus extending equipment lifespan, but also prevents liquid slugging in the magnetic levitation refrigeration compressor caused by excessively high liquid levels and cavitation of the refrigerant pump caused by excessively low liquid levels.

[0007] The technical solution of this invention is as follows:

[0008] On one hand, the present invention provides a magnetic levitation centrifugal chiller unit with a tank pump for liquid supply, including a magnetic levitation refrigeration compressor, a condenser and a low-pressure circulation tank connected in sequence. The low-pressure circulation tank is also connected to an evaporation assembly on the user side. The evaporation assembly includes an evaporator, a working refrigerant pump and a standby refrigerant pump, and the working refrigerant pump is set one-to-one with the evaporator. The liquid refrigerant in the low-pressure circulation tank is transported to the evaporator through the refrigerant pump assembly.

[0009] On the other hand, the present invention also provides a control method for the above-mentioned magnetic levitation centrifugal chiller unit with tank pump liquid supply, including:

[0010] The operating load of the magnetic levitation refrigeration compressor is adjusted according to the relationship between the real-time suction pressure P of the magnetic levitation centrifugal chiller unit and the target pressure set value P0, so that the cooling capacity of the chiller unit matches the cooling load on the user side.

[0011] When the cooling capacity of the chiller unit is mismatched with the cooling load on the user side, causing fluctuations in the liquid level in the low-pressure circulating tank, the operating load of the magnetic levitation refrigeration compressor and the operating frequency of the working refrigerant pump are coordinated and adjusted to maintain the stability of the liquid level in the low-pressure circulating tank.

[0012] According to a preferred embodiment of the present invention, adjusting the operating load of the magnetic levitation refrigeration compressor based on the relationship between the real-time suction pressure P of the magnetic levitation centrifugal chiller unit and the target pressure setpoint P0, so that the cooling capacity of the chiller unit matches the cooling load on the user side, includes:

[0013] When the cooling load on the user side decreases, the real-time suction pressure P is less than the target pressure set value P0, and the magnetic levitation refrigeration compressor operates under reduced load, so that the cooling capacity of the chiller unit matches the load on the user side.

[0014] When the cooling load on the user side increases, the real-time suction pressure P is greater than the target pressure setting value P0, and the magnetic levitation refrigeration compressor is loaded and operated, so that the cooling capacity of the chiller unit matches the load on the user side.

[0015] According to a preferred embodiment of the present invention, the frequency of the magnetic levitation refrigeration compressor is adjusted by PID control so that the real-time suction pressure P is close to the target pressure set value P0, that is, the temperature of the refrigerant in the low-pressure circulation tank is close to the saturation temperature T0 corresponding to the target pressure P0. The sensor for detecting the real-time suction pressure P is installed on the suction pipe of the magnetic levitation refrigeration compressor or on the top of the low-pressure circulation tank.

[0016] According to a preferred embodiment of the present invention, when the cooling capacity of the chiller unit does not match the cooling load on the user side, it will cause fluctuations in the liquid level in the low-pressure circulating tank, including:

[0017] When the load on the user side exceeds the cooling capacity of the chiller unit, the liquid level in the low-pressure circulating tank will drop.

[0018] When the load on the user side is less than the cooling capacity of the chiller, the liquid level in the low-pressure circulating tank will rise.

[0019] According to a preferred embodiment of the present invention, the method of coordinating the operating load of the magnetic levitation refrigeration compressor and the operating frequency of the working refrigerant pump to maintain a stable liquid level in the low-pressure circulation tank includes:

[0020] The highest permissible liquid level for normal operation of the low-pressure circulating tank is H. max The lowest liquid level is H min The actual liquid level is H, the lower limit of the pre-adjusted liquid level is H1, and the upper limit of the second pre-adjusted liquid level is H3;

[0021] When H≤H min When the frequency of the magnetic levitation refrigeration compressor is adjusted by PID control so that the real-time suction pressure P approaches the target pressure set value P0, the working refrigerant pump stops running and a low liquid level alarm is triggered; when H > H1, the low liquid level alarm stops.

[0022] When H min When H ≤ H1, the PID controller adjusts the frequency of the magnetic levitation refrigeration compressor to bring the real-time suction pressure P close to the target pressure setpoint P0, and the working refrigerant pump operates at the set minimum frequency f. min run;

[0023] When H1 < H ≤ H3, the magnetic levitation refrigeration compressor continues to run, and the PID control adjusts the operating frequency of the refrigerant pump to keep the temperature of the evaporator environment close to the target temperature T. s ;

[0024] When H3 < H ≤ H max At this time, the magnetic levitation refrigeration compressor operates under reduced load, increasing the operating frequency of the working refrigerant pump;

[0025] When H > H max When a high liquid level alarm is triggered, the magnetic levitation refrigeration compressor stops, while the working refrigerant pump continues to operate at its highest frequency. max During operation, the liquid level gradually decreases. When the actual liquid level drops to H < H2, the high liquid level alarm stops, and the magnetic levitation refrigeration compressor restarts.

[0026] According to a preferred embodiment of the present invention, the step of continuing to operate the magnetic levitation refrigeration compressor when H1 < H ≤ H3 includes:

[0027] The low-pressure circulation tank is also equipped with a level gauge, and the level gauge is connected in parallel with a level switch; when H1<H≤H2, H2 represents the first pre-adjusted upper limit of the liquid level, and H2<H3, the PID adjusts the frequency of the magnetic levitation refrigeration compressor so that the real-time suction pressure P is close to the target pressure set value P0.

[0028] When H2 < H ≤ H3, the magnetic levitation refrigeration compressor operates under reduced load, and the minimum operating load is not less than the minimum load for high energy efficiency.

[0029] According to a preferred embodiment of the present invention, when H3 < H ≤ H max At this time, the magnetic levitation refrigeration compressor operates under reduced load, increasing the operating frequency of the working refrigerant pump; specifically:

[0030] The magnetic levitation refrigeration compressor operates at high energy efficiency and minimum load, and all working refrigerant pumps operate at the highest frequency. max Continue running.

[0031] According to a preferred embodiment of the present invention, the adjustment of the operating frequency of the working refrigerant pump ensures that the temperature of the environment where the evaporator is located is close to the target temperature T. s ,include:

[0032] The chiller unit consists of N evaporators, and the ambient temperature of the i-th or j-th evaporator is T. i or T j , where i or j is any integer value from 1 to N;

[0033] During the cooling process of the environment where the evaporator is located:

[0034] |T i -T j |>ΔT max When, ΔT max This represents the maximum acceptable temperature difference between different regions on the side of use; for min{T i ,T j The corresponding working refrigerant pump is operated at a reduced frequency.

[0035] |T i -T j |≤ΔT min When, ΔT min Indicates the minimum warning value for temperature difference in different areas on the usage side; PID adjusts the operating frequency of the working refrigerant pump;

[0036] During the stabilization process of the ambient temperature where the evaporator is located: the frequency of the refrigerant pump is adjusted by PID control to ensure that T i and T j Approaching T s .

[0037] According to a preferred embodiment of the present invention, when the actual liquid level H in the low-pressure circulation tank is ≥ H b At that time, and H max <H b H b If the value indicates a high liquid level protection threshold, a high liquid level protection shutdown will be triggered, the magnetic levitation refrigeration compressor will stop running, and all working refrigerant pumps will operate at the highest frequency f. max Continue running.

[0038] The beneficial effects of this invention are as follows:

[0039] This invention provides a magnetic levitation centrifugal chiller unit and control method with a tank pump for liquid supply. It combines the advantages of the oil-free design of the magnetic levitation compressor and the tank pump liquid supply, resulting in a significantly higher energy efficiency ratio than traditional units. Multi-level protection logic is provided for the liquid level in the low-pressure circulating tank. This not only avoids frequent start-stop cycles of the magnetic levitation compressor due to frequent liquid level alarms, extending equipment life, but also prevents liquid slugging in the magnetic levitation compressor due to excessively high liquid levels and cavitation of the refrigerant pump due to excessively low liquid levels. Furthermore, a working refrigerant pump is installed on the user side to supply liquid to the evaporator as needed, and a backup refrigerant pump is designed for redundancy. By adjusting the operating frequency of the working refrigerant pump, the temperature difference between different refrigeration zones on the user side is greatly reduced, resulting in a more uniform temperature distribution. Attached Figure Description

[0040] Figure 1 This invention provides a schematic diagram of the structure of a magnetic levitation centrifugal chiller unit with a barrel pump for liquid supply.

[0041] The components include: 1. Evaporator, 2. Working refrigerant pump, 3. Standby refrigerant pump, 4. Magnetic levitation refrigeration compressor, 5. Low-pressure circulation tank, 6. Condenser, 7. Level gauge, and 8. Level switch. Detailed Implementation

[0042] The following illustrations will disclose several embodiments of this application, providing a clear and complete description of the technical solution of the present invention, which constitutes a part of this application. The accompanying drawings are used to provide a further understanding of the present invention. The illustrative embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. 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.

[0043] It should be noted that the terms "first," "second," and similar terms used in this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Furthermore, in the various embodiments of this disclosure, the same or similar reference numerals denote the same or similar elements.

[0044] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "connection" can refer to a fixed connection, a detachable connection, or an integral part, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0045] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0046] Example 1

[0047] This embodiment provides a magnetic levitation centrifugal chiller unit with a tank pump for liquid supply, such as... Figure 1 As shown, the system includes a magnetic levitation refrigeration compressor 4, a condenser 6, and a low-pressure circulation tank 5 connected in sequence. The low-pressure circulation tank 5 is also connected to the evaporation assembly on the user side. The evaporation assembly includes an evaporator 1, a working refrigerant pump 2, and a standby refrigerant pump 3, with the working refrigerant pump 2 corresponding to the evaporator 1 in a one-to-one manner. The working refrigerant pump 2 adjusts the liquid supply to the evaporator 1 by adjusting its operating frequency. The gaseous refrigerant above the low-pressure circulation tank 5 is drawn in and compressed by the magnetic levitation refrigeration compressor 4, then enters the condenser 6 and condenses into liquid refrigerant, which is then transported to the low-pressure circulation tank 5. The liquid refrigerant in the low-pressure circulation tank 5 is transported to the evaporator 1 by the refrigerant pump assembly.

[0048] Example 2

[0049] This embodiment provides a control method for the magnetic levitation centrifugal chiller unit with tank pump liquid supply as described in Embodiment 1, including:

[0050] The operating load of the magnetic levitation compressor 4 is adjusted according to the relationship between the real-time suction pressure P of the magnetic levitation centrifugal chiller unit and the target pressure set value P0, so that the cooling capacity of the chiller unit matches the cooling load on the user side.

[0051] When the cooling capacity of the chiller unit is mismatched with the cooling load on the user side, causing fluctuations in the liquid level in the low-pressure circulation tank 5, the operating load of the magnetic levitation refrigeration compressor 4 and the operating frequency of the working refrigerant pump 2 are coordinated and adjusted to maintain the stability of the liquid level in the low-pressure circulation tank 5.

[0052] The form of evaporator 1 is not limited to condenser coils, air coolers, or flooded evaporators. The control details differ depending on the form of evaporator used, but the core control method is the same as described above.

[0053] Example 3

[0054] This embodiment provides a control method for a magnetic levitation centrifugal chiller unit with a tank pump for liquid supply, which differs from Embodiment 2 in that:

[0055] The method of adjusting the operating load of the magnetic levitation refrigeration compressor 4 based on the relationship between the real-time suction pressure P of the magnetic levitation centrifugal chiller unit and the target pressure setpoint P0, so that the cooling capacity of the chiller unit matches the cooling load on the user side, includes:

[0056] When the cooling load on the user side decreases, the real-time suction pressure P is less than the target pressure setting value P0, and the magnetic levitation refrigeration compressor 4 operates under reduced load, so that the cooling capacity of the chiller unit matches the load on the user side.

[0057] When the cooling load on the user side increases, the real-time suction pressure P is greater than the target pressure setting value P0, and the magnetic levitation refrigeration compressor 4 is loaded and operated, so that the cooling capacity of the chiller unit matches the load on the user side.

[0058] Example 4

[0059] This embodiment provides a control method for a magnetic levitation centrifugal chiller unit with a tank pump for liquid supply, which differs from Embodiment 3 in that:

[0060] The frequency of the magnetic levitation refrigeration compressor 4 is adjusted by PID control so that the real-time suction pressure P is close to the target pressure set value P0, that is, the temperature of the refrigerant in the low-pressure circulation tank 5 is close to the saturation temperature T0 corresponding to the target pressure P0. The sensor for detecting the real-time suction pressure P is installed on the suction pipe of the magnetic levitation refrigeration compressor 4 or on the top of the low-pressure circulation tank 5.

[0061] The target temperature of the environment where evaporator group 1 is located is T S The target temperature of the refrigerant in the low-pressure circulation tank 5 is T0, where T0 is the temperature corresponding to the saturation pressure P0. The heat exchange temperature difference between the target temperature of the refrigerant in the low-pressure circulation tank 5 and the ambient temperature of the evaporator group 1 is denoted by ΔT, where ΔT = T S -T0. To ensure good cooling performance and economy of the refrigeration system, ΔT is usually taken as about 5℃.

[0062] Example 5

[0063] This embodiment provides a control method for a magnetic levitation centrifugal chiller unit with a tank pump for liquid supply, which differs from Embodiment 2 in that:

[0064] When the cooling capacity of the chiller unit does not match the cooling load on the user side, it will cause fluctuations in the liquid level in the low-pressure circulating tank 5, including:

[0065] When the load on the user side exceeds the cooling capacity of the chiller unit, the liquid level in the low-pressure circulation tank 5 will drop.

[0066] When the load on the user side is less than the cooling capacity of the chiller unit, the liquid level in the low-pressure circulation tank 5 will rise.

[0067] The large volume of the low-pressure circulation tank 5 can significantly alleviate the fluctuation of the liquid level in the low-pressure circulation tank 5 when the load on the operating side does not match the cooling capacity of the unit, thus avoiding frequent start-stop of the magnetic levitation refrigeration compressor 4 and the refrigerant pump due to frequent triggering of the liquid level alarm and extending the service life of the equipment.

[0068] Example 6

[0069] This embodiment provides a control method for a magnetic levitation centrifugal chiller unit with a tank pump for liquid supply, which differs from Embodiment 2 in that:

[0070] The coordinated regulation of the operating load of the magnetic levitation refrigeration compressor 4 and the operating frequency of the working refrigerant pump 2 to maintain a stable liquid level in the low-pressure circulation tank 5 includes:

[0071] The low-pressure circulation tank 5 is also equipped with a level gauge 7, and a level switch 8 is connected in parallel with the level gauge 7; the highest allowable liquid level for normal operation of the low-pressure circulation tank 5 is H. max The lowest liquid level is H min The actual liquid level is H, the lower limit of the pre-adjusted liquid level is H1, and the upper limit of the second pre-adjusted liquid level is H3;

[0072] When H≤H min When the working refrigerant pump 2 is at risk of cavitation, the frequency of the magnetic levitation refrigeration compressor 4 is adjusted by PID control so that the real-time suction pressure P is close to the target pressure set value P0. The working refrigerant pump 2 stops running and a low liquid level alarm is triggered. The purpose is to raise the liquid level in the low-pressure circulation tank 5. When H > H1, the low liquid level alarm stops.

[0073] When H min When H ≤ H1, the PID controller adjusts the frequency of the magnetic levitation compressor 4 to bring the real-time suction pressure P close to the target pressure setpoint P0, and the working refrigerant pump 2 operates at the set minimum frequency f. min Running; minimum frequency f min The determination can be made based on the on-site commissioning situation. The aim is to ensure the minimum cooling capacity of the working refrigerant pump 2 while simultaneously increasing the liquid level in the low-pressure circulation tank 5.

[0074] When H1 < H ≤ H3, the magnetic levitation refrigeration compressor 4 continues to operate, and the PID control adjusts the operating frequency of the refrigerant pump 2 to keep the temperature of the environment where the evaporator 1 is located close to the target temperature T. s ;

[0075] When H3 < H ≤ H max At this time, the magnetic levitation refrigeration compressor 4 operates under reduced load, increasing the operating frequency of the working refrigerant pump 2;

[0076] When H > H max If the magnetic levitation refrigeration compressor 4 has a risk of liquid carryover during suction, a high liquid level alarm will be triggered, the magnetic levitation refrigeration compressor 4 will stop, and the working refrigerant pump 2 will continue to operate at the highest frequency. max During operation, the liquid level gradually decreases. When the actual liquid level drops to H < H2, the high liquid level alarm stops, and the magnetic levitation refrigeration compressor 4 restarts.

[0077] In addition, if any of the working fluorine pumps 2 fails, the backup fluorine pump 3 will be started and controlled using the control method of the failed working fluorine pump 2.

[0078] Example 7

[0079] This embodiment provides a control method for a magnetic levitation centrifugal chiller unit with a tank pump for liquid supply, which differs from Embodiment 6 in that:

[0080] When H1 < H ≤ H3, the magnetic levitation refrigeration compressor 4 continues to operate, and the PID control adjusts the operating frequency of the refrigerant pump 2 to bring the ambient temperature of the evaporator 1 close to the target temperature T. s ;include:

[0081] When H1 < H ≤ H2, H2 represents the upper limit of the first pre-adjusted liquid level, and H2 < H3. The PID adjusts the frequency of the magnetic levitation refrigeration compressor 4 so that the real-time suction pressure P is close to the target pressure setpoint P0; the PID adjusts the operating frequency of the working refrigerant pump 2 so that the temperature of the environment where the evaporator 1 is located is close to the target temperature T. s ;

[0082] When H2 < H ≤ H3, the magnetic levitation refrigeration compressor 4 operates under reduced load, and the minimum operating load is not less than the high-efficiency minimum load, thereby maintaining the high refrigeration efficiency of the magnetic levitation refrigeration compressor 4. The high-efficiency minimum load of the magnetic levitation centrifugal chiller unit varies depending on the design of the unit, but is generally around 30%. PID control of the operating frequency of the refrigerant pump 2 ensures that the temperature of the environment where the evaporator 1 is located is close to the target temperature T. s .

[0083] Example 8

[0084] This embodiment provides a control method for a magnetic levitation centrifugal chiller unit with a tank pump for liquid supply, which differs from Embodiment 6 in that:

[0085] When H3 < H ≤ H max At this time, the magnetic levitation refrigeration compressor 4 operates under reduced load, increasing the operating frequency of the working refrigerant pump 2; specifically:

[0086] The magnetic levitation refrigeration compressor 4 operates at high efficiency and minimum load, and all working refrigerant pumps 2 operate at the highest frequency f. max Continue operation. To maintain the chiller unit's high cooling efficiency and avoid it entering a low-load, low-efficiency operating state.

[0087] Example 9

[0088] This embodiment provides a control method for a magnetic levitation centrifugal chiller unit with a tank pump for liquid supply, which differs from Embodiment 6 in that:

[0089] The operating frequency of the fluorine pump 2 is adjusted so that the temperature of the environment where the evaporator 1 is located is close to the target temperature T. s ,include:

[0090] The chiller unit includes N evaporators 1, and the ambient temperature of the i-th or j-th evaporator 1 is T. i or T j , where i or j is any integer value from 1 to N;

[0091] During the cooling process of the environment where evaporator 1 is located: the cooling load on the user side fluctuates greatly, such as during the loading and unloading of goods in the cold storage.

[0092] |T i -T j |>ΔT max When, ΔT max This represents the maximum acceptable temperature difference between different regions on the side of use; for min{T i ,T j The corresponding working refrigerant pump 2 operates at a reduced frequency; in this case, manual intervention is introduced to ensure the temperature consistency of different evaporator 1 areas, and PID regulation is temporarily not used.

[0093] It should be noted that the above design is implemented for large-scale cooling applications where high temperature uniformity is required, in order to avoid excessive differences in temperature drop in different areas during the cooling process, which would lead to uneven temperature distribution.

[0094] |T i -T j |≤ΔT min When, ΔT min Indicates the minimum warning value for temperature difference in different areas on the usage side; PID adjusts the operating frequency of working refrigerant pump 2; ΔT min and ΔT max The design avoids frequent switching of PID control.

[0095] During periods when the ambient temperature of evaporator 1 is stable: the cooling load fluctuation on the user side is relatively small, such as during cold storage; the refrigerant pump frequency is adjusted via PID control to ensure T i and T j Approaching T s T and T j Approaching T s This can be understood as: T i =T s ±0.5℃, T j =T s ±0.5℃; Each evaporator circuit corresponding to a refrigerant pump is equipped with an independent closed-loop PID controller.

[0096] Example 10

[0097] This embodiment provides a control method for a magnetic levitation centrifugal chiller unit with a tank pump for liquid supply, which differs from Embodiment 6 in that:

[0098] Due to reasons such as liquid level sensor malfunction, when H > H max If this happens, the high liquid level alarm may not be triggered and the compressor 4 continues to run, causing the liquid level to continue rising. To avoid this situation, when the actual liquid level H in the low-pressure circulation tank 5 is ≥ H... b At that time, and H max <H b H b If the high liquid level protection value is indicated, the liquid level switch 8 is triggered, initiating a high liquid level protection shutdown. The magnetic levitation refrigeration compressor 4 stops running, and all operating refrigerant pumps 2 operate at the highest frequency f. max If the system continues to operate, and the high liquid level protection shuts down, the cause of the fault must be investigated on-site and the system manually reset.

[0099] The foregoing description illustrates and describes preferred embodiments of this application. However, as previously understood, this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the conception herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.

Claims

1. A magnetic levitation centrifugal chiller unit with a tank pump for liquid supply, characterized in that, It includes a magnetic levitation refrigeration compressor, a condenser, and a low-pressure circulation tank connected in sequence. The low-pressure circulation tank is also connected to the evaporation assembly on the user side. The evaporation assembly includes an evaporator, a working refrigerant pump, and a standby refrigerant pump, with the working refrigerant pump and the evaporator being set up one-to-one. The liquid refrigerant in the low-pressure circulation tank is transported to the evaporator through the refrigerant pump group. The unit is configured as follows: The operating load of the magnetic levitation refrigeration compressor is adjusted according to the relationship between the real-time suction pressure P of the magnetic levitation centrifugal chiller unit and the target pressure set value P0, so that the cooling capacity of the chiller unit matches the cooling load on the user side. When the cooling capacity of the chiller unit is mismatched with the cooling load on the user side, causing fluctuations in the liquid level in the low-pressure circulating tank, the operating load of the magnetic levitation refrigeration compressor and the operating frequency of the working refrigerant pump are coordinated and adjusted to maintain the stability of the liquid level in the low-pressure circulating tank.

2. The control method for a magnetically levitated centrifugal chiller unit with a tank pump supply according to claim 1, characterized in that, include: The operating load of the magnetic levitation refrigeration compressor is adjusted according to the relationship between the real-time suction pressure P of the magnetic levitation centrifugal chiller unit and the target pressure set value P0, so that the cooling capacity of the chiller unit matches the cooling load on the user side. When the cooling capacity of the chiller unit is mismatched with the cooling load on the user side, causing fluctuations in the liquid level in the low-pressure circulating tank, the operating load of the magnetic levitation refrigeration compressor and the operating frequency of the working refrigerant pump are coordinated and adjusted to maintain the stability of the liquid level in the low-pressure circulating tank.

3. The control method for a magnetically levitated centrifugal chiller unit with a tank pump for liquid supply according to claim 2, characterized in that, The operating load of the magnetic levitation refrigeration compressor is adjusted according to the relationship between the real-time suction pressure P of the magnetic levitation centrifugal chiller unit and the target pressure set value P0, so that the cooling capacity of the chiller unit matches the cooling load on the user side. include: When the cooling load on the user side decreases, the real-time suction pressure P is less than the target pressure set value P0, and the magnetic levitation refrigeration compressor operates under reduced load, so that the cooling capacity of the chiller unit matches the load on the user side. When the cooling load on the user side increases, the real-time suction pressure P is greater than the target pressure setting value P0, and the magnetic levitation refrigeration compressor is loaded and operated, so that the cooling capacity of the chiller unit matches the load on the user side.

4. The control method for a magnetically levitated centrifugal chiller unit with a tank pump supply according to claim 3, characterized in that, The frequency of the magnetic levitation refrigeration compressor is adjusted by PID control so that the real-time suction pressure P is close to the target pressure setpoint P0, that is, the temperature of the refrigerant in the low-pressure circulation tank is close to the saturation temperature T0 corresponding to the target pressure P0. The sensor that detects the real-time suction pressure P is installed on the suction pipe of the magnetic levitation refrigeration compressor or on the top of the low-pressure circulation tank.

5. The control method for a magnetically levitated centrifugal chiller unit with a tank pump supply according to claim 2, characterized in that, When the cooling capacity of the chiller unit does not match the cooling load on the user side, it will cause fluctuations in the liquid level in the low-pressure circulating tank, including: When the load on the user side exceeds the cooling capacity of the chiller unit, the liquid level in the low-pressure circulating tank will drop. When the load on the user side is less than the cooling capacity of the chiller, the liquid level in the low-pressure circulating tank will rise.

6. The control method for a magnetically levitated centrifugal chiller unit with a tank pump for liquid supply according to claim 2, characterized in that, The coordinated regulation of the operating load of the magnetic levitation refrigeration compressor and the operating frequency of the working refrigerant pump to maintain a stable liquid level in the low-pressure circulation tank includes: The highest permissible liquid level for normal operation of the low-pressure circulating tank is H. max The lowest liquid level is H min The actual liquid level is H, the lower limit of the pre-adjusted liquid level is H1, and the upper limit of the second pre-adjusted liquid level is H3; When H≤H min When the frequency of the magnetic levitation refrigeration compressor is adjusted by PID control so that the real-time suction pressure P approaches the target pressure set value P0, the working refrigerant pump stops running and a low liquid level alarm is triggered; when H > H1, the low liquid level alarm stops. When H min When H ≤ H1, the PID controller adjusts the frequency of the magnetic levitation refrigeration compressor to bring the real-time suction pressure P close to the target pressure setpoint P0, and the working refrigerant pump operates at the set minimum frequency. f min run; When H1 < H ≤ H3, the magnetic levitation refrigeration compressor continues to run, and the PID control adjusts the operating frequency of the refrigerant pump to keep the temperature of the evaporator environment close to the target temperature T. s ; When H3 < H ≤ H max At this time, the magnetic levitation refrigeration compressor operates under reduced load, increasing the operating frequency of the working refrigerant pump; When H > H max When a high liquid level alarm is triggered, the magnetic levitation refrigeration compressor stops, while the working refrigerant pump continues to operate at the highest frequency. f max During operation, the liquid level gradually decreases. When the actual liquid level drops to H < H2, the high liquid level alarm stops, and the magnetic levitation refrigeration compressor restarts.

7. The control method for a magnetically levitated centrifugal chiller unit with a tank pump supply according to claim 6, characterized in that, The condition that the magnetic levitation refrigeration compressor continues to operate when H1 < H ≤ H3 includes: When H1 < H ≤ H2, H2 represents the first pre-adjusted upper limit of the liquid level, and H2 < H3, the PID adjusts the frequency of the magnetic levitation refrigeration compressor so that the real-time suction pressure P is close to the target pressure set value P0. When H2 < H ≤ H3, the magnetic levitation refrigeration compressor operates under reduced load, and the minimum operating load is not less than the minimum load for high energy efficiency.

8. The control method for a magnetically levitated centrifugal chiller unit with a tank pump supply according to claim 6, characterized in that, When H3 < H ≤ H max At this time, the magnetic levitation refrigeration compressor operates under reduced load, increasing the operating frequency of the working refrigerant pump; specifically: The magnetic levitation refrigeration compressor operates at high energy efficiency and minimum load, while all working refrigerant pumps continue to operate at the highest frequency fmax.

9. The control method for a magnetically levitated centrifugal chiller unit with a tank pump supply according to claim 6, characterized in that, The operating frequency of the working refrigerant pump is adjusted so that the temperature of the environment where the evaporator is located is close to the target temperature T. s ,include: The chiller unit consists of N evaporators, and the ambient temperature of the i-th or j-th evaporator is T. i or T j , where i or j is any integer value from 1 to N; During the cooling process of the environment where the evaporator is located: |T i -T j |>ΔT max When, ΔT max This represents the maximum acceptable temperature difference between different regions on the side of use; for min{ T i ,T j The corresponding working refrigerant pump will operate at a reduced frequency. |T i -T j |≤ΔT min When, ΔT min Indicates the minimum warning value for temperature difference in different areas on the usage side; PID adjusts the operating frequency of the working refrigerant pump; During the stabilization process of the ambient temperature where the evaporator is located: the frequency of the refrigerant pump is adjusted by PID control to ensure that T i and T j Approaching T s .

10. The control method for a magnetically levitated centrifugal chiller unit with a tank pump supply according to claim 6, characterized in that, When the actual liquid level H in the low-pressure circulation tank is greater than or equal to H b At that time, and H max <H b H b If the value indicates a high liquid level protection threshold, a high liquid level protection shutdown will be triggered, the magnetic levitation refrigeration compressor will stop running, and all working refrigerant pumps will operate at the highest frequency f. max Continue running.

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