Magnetic suspension centrifugal water chilling unit based on thermosyphon cooling and control method

Abstract

According to the magnetic suspension centrifugal water chilling unit based on thermosyphon cooling and the control method, a refrigerant is evaporated through an evaporator, compressed through a magnetic suspension refrigeration compressor and condensed through an evaporative condenser in sequence and then flows into a thermosyphon tank from the evaporative condenser, and when the liquid refrigerant in the thermosyphon tank exceeds the set liquid level, the liquid refrigerant in the thermosyphon tank flows into the magnetic suspension centrifugal water chilling unit based on thermosyphon cooling; a liquid refrigerant sequentially flows through the liquid storage device, the first expansion valve and the evaporator, circulation is carried out, and main refrigeration circulation of the magnetic suspension centrifugal water chilling unit is completed. The first cooling channel is arranged for the magnetic suspension refrigeration compressor, power-consumption-free heat dissipation of the magnetic suspension refrigeration compressor is achieved through the thermosyphon effect of refrigerants, compared with a conventional heat dissipation scheme, the refrigerating capacity loss of a main refrigeration cycle in the water chilling unit is reduced, and the energy efficiency of the magnetic suspension water chilling unit is improved; and thermosyphon circulating cooling is continuously and automatically carried out, and the heat dissipation effect is stable and reliable. And meanwhile, the second cooling channel is arranged to ensure the cooling effect of the magnetic suspension refrigeration compressor under special conditions.

Description

Technical Field

[0001] The present invention relates to a magnetic levitation centrifugal chiller based on thermosiphon cooling and a control method thereof, belonging to the technical field of heat dissipation of magnetic levitation centrifugal chillers. Background Art

[0002] A magnetic levitation centrifugal chiller is an oil-free system that uses a refrigerant to cool the motor of the magnetic levitation refrigeration compressor. Currently, the conventional motor cooling solution is to use the refrigerant flowing out of the condenser or high-pressure liquid receiver. After being regulated and controlled by the solenoid valve and throttle valve, it enters the motor cooling channel of the magnetic levitation refrigeration compressor. The refrigerant absorbs the heat of the motor and vaporizes, and then enters the intake end of the magnetic levitation refrigeration compressor or the evaporator. After being sucked and compressed by the magnetic levitation refrigeration compressor, the subsequent refrigeration cycle is carried out. This part of the refrigerant used for cooling the magnetic levitation refrigeration compressor can neither provide cooling capacity for users nor consume compression work, so it will reduce the energy efficiency of the magnetic levitation centrifugal chiller.

[0003] How to reduce the effective cooling capacity and power consumption consumed by cooling the magnetic levitation refrigeration compressor, while improving the cooling effect of the magnetic levitation refrigeration compressor and the stability of the motor temperature, is of great significance for improving the refrigeration energy efficiency of the magnetic levitation centrifugal chiller and ensuring the safe operation of the motor. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a magnetic levitation centrifugal chiller based on thermosiphon cooling and a control method thereof. A first cooling channel is provided in the magnetic levitation centrifugal chiller to cool the magnetic levitation refrigeration compressor. The thermosiphon effect of the refrigerant is utilized in the first cooling channel to achieve power-free heat dissipation, without passing through the suction and compression of the magnetic levitation refrigeration compressor. Compared with the conventional cooling solution, the cooling capacity loss and compressor power consumption of the magnetic levitation centrifugal chiller are reduced.

[0005] The technical solution of the present invention is as follows: A magnetic levitation centrifugal chiller based on thermosiphon cooling, comprising a magnetic levitation refrigeration compressor, an evaporative condenser, a thermosiphon tank, a liquid receiver, a first expansion valve, and an evaporator connected in sequence; In the main refrigeration cycle of the magnetic levitation centrifugal chiller, the gaseous refrigerant output from the evaporator is compressed by the magnetic levitation refrigeration compressor and condensed by the evaporative condenser to become a liquid refrigerant. The liquid refrigerant then flows from the evaporative condenser into the thermosiphon tank. When the liquid refrigerant in the thermosiphon tank exceeds the set liquid level, the liquid refrigerant flows through the liquid receiver, the first expansion valve, and the evaporator in sequence, and circulates repeatedly to complete the main refrigeration cycle of the magnetic levitation centrifugal chiller; A first cooling channel is also provided between the thermosyphon tank and the magnetic levitation refrigeration compressor. By utilizing the thermosyphon effect, the refrigerant in the magnetic levitation refrigeration compressor circulates between the thermosyphon tank and the magnetic levitation refrigeration compressor, realizing the cooling of the magnetic levitation refrigeration compressor.

[0006] Preferably according to the present invention, a first liquid outlet pipe and a first return pipe are respectively arranged between the thermosyphon tank and the magnetic levitation refrigeration compressor. The first liquid outlet pipe and the first return pipe are respectively communicated with the inlet and the outlet of the first refrigerant channel in the magnetic levitation refrigeration compressor. The thermosyphon tank, the first liquid outlet pipe, the magnetic levitation refrigeration compressor and the first return pipe are communicated to form a first cooling channel.

[0007] Preferably according to the present invention, a first liquid inlet pipe is arranged between the evaporative condenser and the thermosyphon tank, an exhaust pipe is arranged between the magnetic levitation refrigeration compressor and the evaporative condenser, and the thermosyphon tank is also communicated with the exhaust pipe through an exhaust bypass pipe.

[0008] Preferably according to the present invention, the magnetic levitation centrifugal chiller is also provided with a second cooling channel. A second liquid outlet pipe is arranged between the liquid storage tank and the magnetic levitation refrigeration compressor. A solenoid valve and a second expansion valve are arranged on the second liquid outlet pipe. A second return pipe is arranged between the magnetic levitation refrigeration compressor and the evaporator. And the second liquid outlet pipe and the second return pipe are respectively communicated with the inlet and the outlet of the second refrigerant channel in the magnetic levitation refrigeration compressor. The liquid storage tank, the second liquid outlet pipe, the magnetic levitation refrigeration compressor, the second return pipe and the evaporator form a second cooling channel.

[0009] Preferably according to the present invention, a drain pipe is arranged between the thermosyphon tank and the liquid storage tank; a liquid return pipe is arranged between the liquid storage tank and the evaporator, and a first expansion valve is arranged on the liquid return pipe.

[0010] Preferably according to the present invention, the installation position of the evaporative condenser needs to be higher than the installation position of the thermosyphon tank, and the installation position of the thermosyphon tank is higher than the installation position of the liquid storage tank.

[0011] Preferably according to the present invention, the installation position of the thermosyphon tank is higher than the installation position of the magnetic levitation refrigeration compressor, and it is satisfied that the pipeline resistance in the first cooling channel is less than the driving force generated by the thermosyphon effect.

[0012] The control method of the above-mentioned magnetic levitation centrifugal chiller based on thermosyphon cooling includes: Connect the first cooling channel and start the magnetic levitation refrigeration compressor. Under the thermosiphon effect, the liquid refrigerant flowing out of the thermosiphon tank absorbs the heat of the magnetic levitation refrigeration compressor and vaporizes to form a gas-liquid mixture state, and then flows back to the thermosiphon tank, circulating between the magnetic levitation refrigeration compressor and the thermosiphon tank to achieve the cooling of the magnetic levitation refrigeration compressor; the gaseous refrigerant flowing back into the thermosiphon tank enters the evaporative condenser under the action of pressure difference and condenses into liquid refrigerant, and the liquid refrigerant in the evaporative condenser is transported back to the thermosiphon tank again under the action of gravity; When the liquid refrigerant level in the thermosiphon tank exceeds the set height, the liquid refrigerant is transported to the liquid storage tank to continue the main refrigeration cycle of the magnetic levitation centrifugal chiller.

[0013] Preferably according to the present invention, a solenoid valve is further provided on the second liquid outlet pipe, and the control method further includes: Real-time monitor the motor temperature T of the magnetic levitation refrigeration compressor. When T≥the first set threshold value T1, open the solenoid valve and the expansion valve on the second liquid outlet pipe to connect the second cooling channel; When T<T2 and T2<T1, close the solenoid valve and the expansion valve on the second liquid outlet pipe, and the second cooling channel stops operating. T2 represents the second set threshold value, which is set based on the lower temperature limit for the stable operation of the magnetic levitation centrifugal chiller.

[0014] The beneficial effects of the present invention are: In the present invention, the first cooling channel of the magnetic levitation refrigeration compressor uses the thermosiphon effect to achieve power-free heat dissipation, reducing the cooling capacity loss of the main refrigeration cycle of the magnetic levitation centrifugal chiller. The magnitude of the thermosiphon cooling capacity is positively correlated with the heat generation of the magnetic levitation refrigeration compressor. When the heat generation of the magnetic levitation refrigeration compressor is large, the thermosiphon cycle cooling capacity is strong; when the heat generation of the magnetic levitation refrigeration compressor is small, the thermosiphon cycle cooling capacity is weak. Using the thermosiphon effect of the refrigerant to cool the magnetic levitation refrigeration compressor is beneficial for the motor temperature to automatically tend to the normal range when operating at different powers. In addition, the temperature range of the refrigerant entering the first cooling channel is generally between 20~36℃, with small temperature fluctuations; when the temperature of the magnetic levitation refrigeration compressor is higher than the temperature of the refrigerant in the first cooling channel, the thermosiphon cycle cooling is automatically carried out without interruption, and the heat dissipation effect is stable and reliable.

[0015] The second cooling channel is only enabled when necessary, avoiding additional energy consumption and ensuring the overall energy efficiency improvement of the unit. The first cooling channel uses the thermosiphon effect as the main cooling cycle to achieve uninterrupted and power-free heat dissipation; the second cooling channel serves as an auxiliary cooling cycle, with an intelligent opening and closing function, achieving efficient heat dissipation of the magnetic levitation refrigeration compressor while reducing system energy consumption. Description of the Drawings

[0016] Figure 1Schematic diagram of the structure of the magnetic levitation centrifugal chiller based on thermosiphon cooling provided by the present invention.

[0017] 1. Magnetic levitation refrigeration compressor, 2. Evaporative condenser, 3. Liquid receiver, 4. Evaporator, 5. Thermosiphon tank, 6. First liquid discharge pipe, 7. First return pipe, 8. Second liquid discharge pipe, 9. Second return pipe, 10. Exhaust bypass pipe, 11. First liquid inlet pipe, 12. Liquid return pipe, 13. Solenoid valve, 14. First expansion valve. 15. Liquid drain pipe, 16. Exhaust pipe, 17. Second expansion valve. Specific embodiments

[0018] The following will disclose several embodiments of the present application in the form of diagrams, and clearly and completely describe the technical solutions of the present invention, which form a part of the present application. The accompanying drawings of the specification 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 in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0019] It should be noted that unless otherwise defined specifically, the up, down, left, right and other directions involved herein are based on the up, down, left, right and other directions shown in the embodiments of the present application Figure 1 If the specific posture changes, the directional indication will also change accordingly. The "first", "second" and similar terms used in the present application do not indicate any order, quantity or importance, but are only used to distinguish different components. In addition, in each embodiment of the present disclosure, the same or similar reference numerals represent the same or similar components.

[0020] In the present invention, unless otherwise clearly defined and limited, terms such as "connection" and "fixation" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral one, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0021] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0022] Embodiment 1 This embodiment provides a magnetic levitation centrifugal chiller based on thermosiphon cooling, as Figure 1As shown, it includes a magnetic levitation refrigeration compressor 1, an evaporative condenser 2, a thermosyphon tank 5, a liquid receiver 3, a first expansion valve 14, and an evaporator 4 connected in sequence; In the main refrigeration cycle of the magnetic levitation centrifugal chiller, the gaseous refrigerant output from the evaporator 4 is compressed by the magnetic levitation refrigeration compressor 1 and condensed by the evaporative condenser 2 to become a liquid refrigerant. The liquid refrigerant then flows from the evaporative condenser 2 into the thermosyphon tank 5. After the liquid refrigerant in the thermosyphon tank 5 exceeds the set liquid level, the liquid refrigerant flows through the liquid receiver 3, the first expansion valve 14, and the evaporator 4 in sequence, and circulates repeatedly to complete the main refrigeration cycle of the magnetic levitation centrifugal chiller; A first cooling channel is also provided between the thermosyphon tank 5 and the magnetic levitation refrigeration compressor 1. Using the thermosyphon effect, the refrigerant in the magnetic levitation refrigeration compressor 1 circulates between the thermosyphon tank 5 and the magnetic levitation refrigeration compressor 1 to achieve the cooling of the magnetic levitation refrigeration compressor 1.

[0023] The liquid refrigerant at the bottom of the thermosyphon tank 5 enters the first cooling channel of the magnetic levitation refrigeration compressor 1 through the first liquid outlet pipe 6. The heat generated by the magnetic levitation refrigeration compressor 1 exchanges heat with the liquid refrigerant. Part of the liquid refrigerant absorbs heat and vaporizes into a gaseous refrigerant, resulting in a decrease in the density of the first return pipe 7. Under the action of the density difference, a thermosyphon driving force is formed to push the refrigerant to circulate, so that the heat-absorbed gas-liquid mixed refrigerant returns to the thermosyphon tank 5 to complete the cooling cycle in the first cooling channel of the magnetic levitation refrigeration compressor 1.

[0024] Using the thermosyphon effect of the refrigerant to dissipate heat from the magnetic levitation refrigeration compressor 1 is equivalent to releasing the heat of the magnetic levitation refrigeration compressor 1 to the outdoor environment through the circulation of the refrigerant, without consuming the refrigeration capacity of the magnetic levitation centrifugal chiller itself and the power consumption of the magnetic levitation refrigeration compressor 1, which helps to improve the refrigeration energy efficiency of the magnetic levitation centrifugal chiller.

[0025] Embodiment 2 The magnetic levitation centrifugal chiller provided in this embodiment based on thermosyphon cooling is different from Embodiment 1 in that: As Figure 1 shown, a first liquid outlet pipe 6 and a first return pipe 7 are respectively provided between the thermosyphon tank 5 and the magnetic levitation refrigeration compressor 1. The first liquid outlet pipe 6 and the first return pipe 7 are respectively connected to the inlet and the outlet of the first refrigerant channel in the magnetic levitation refrigeration compressor 1. The thermosyphon tank 5, the first liquid outlet pipe 6, the magnetic levitation refrigeration compressor 1, and the first return pipe 7 are connected to form a first cooling channel. The first cooling channel plays a main cooling role for the magnetic levitation refrigeration compressor 1. The refrigerant entering the first cooling channel only flows in the first cooling channel, and the first cooling channel is not connected to the cavity of the magnetic levitation refrigeration compressor 1. Among them, the first refrigerant channel is not marked in the drawings.

[0026] Example 3 This embodiment provides a magnetic levitation centrifugal chiller based on thermosiphon cooling, which is different from Embodiment 2 in that: A first liquid inlet pipe 11 is provided between the evaporative condenser 2 and the thermosiphon tank 5, an exhaust pipe 16 is provided between the magnetic levitation refrigeration compressor 1 and the evaporative condenser 2, and the thermosiphon tank 5 is also connected to the exhaust pipe 16 through an exhaust bypass pipe 10. Driven by the pressure difference, the gaseous refrigerant in the thermosiphon tank 5 passes through the exhaust bypass pipe 10 and the exhaust pipe 16, and then enters the evaporative condenser 2 for condensation. After being condensed into a liquid refrigerant, it flows back into the thermosiphon tank 5 again through the first liquid inlet pipe 11, and circulates in turn. The exhaust bypass pipe 10 is used to introduce the gaseous refrigerant in the thermosiphon tank 5 into the exhaust pipe 16 to maintain the pressure stability in the thermosiphon tank 5.

[0027] Example 4 This embodiment provides a magnetic levitation centrifugal chiller based on thermosiphon cooling, which is different from Embodiment 2 in that: As Figure 1 shown, the magnetic levitation centrifugal chiller is further provided with a second cooling channel. A second liquid outlet pipe 8 is provided between the liquid storage tank 3 and the magnetic levitation refrigeration compressor 1. An electromagnetic valve 13 and a second expansion valve 17 are provided on the second liquid outlet pipe 8. A second return pipe 9 is provided between the magnetic levitation refrigeration compressor 1 and the evaporator 4. And the second liquid outlet pipe 8 and the second return pipe 9 are respectively connected to the inlet and the outlet of the second refrigerant channel in the magnetic levitation refrigeration compressor 1. The liquid storage tank 3, the second liquid outlet pipe 8, the magnetic levitation refrigeration compressor 1, the second return pipe 9 and the evaporator 4 form a second cooling channel.

[0028] The liquid refrigerant output by the liquid storage tank 3 enters the second liquid outlet pipe 8, is throttled by the second expansion valve 17 and then enters the inlet of the second refrigerant channel of the magnetic levitation refrigeration compressor 1. The refrigerant absorbs heat in the second refrigerant channel, then flows out from the outlet of the second refrigerant channel, and then returns to the evaporator 4 through the second return pipe 9. The gaseous refrigerant output by the evaporator 4 then enters the intake end of the magnetic levitation refrigeration compressor 1 for compression, entering the path of the main refrigeration cycle.

[0029] The second cooling channel assists in cooling the magnetic levitation refrigeration compressor 1 to ensure the cooling effect of the magnetic levitation refrigeration compressor 1. The second refrigerant channel is not marked in the drawings.

[0030] Example 5 This embodiment provides a magnetic levitation centrifugal chiller based on thermosiphon cooling, which is different from Embodiment 4 in that: As Figure 1As shown, a drain pipe 15 is provided between the thermosyphon tank 5 and the liquid reservoir 3; a return pipe 12 is provided between the liquid reservoir 3 and the evaporator 4, and a first expansion valve 14 is provided on the return pipe 12.

[0031] Embodiment 6 This embodiment provides a magnetic levitation centrifugal chiller based on thermosyphon cooling, which is different from Embodiment 4 in that: The installation position of the evaporative condenser 2 needs to be higher than the installation position of the thermosyphon tank 5, and the installation position of the thermosyphon tank 5 is higher than the installation position of the liquid reservoir 3.

[0032] Embodiment 7 This embodiment provides a magnetic levitation centrifugal chiller based on thermosyphon cooling, which is different from Embodiment 4 in that: The installation position of the thermosyphon tank 5 is higher than the installation position of the magnetic levitation refrigeration compressor 1, and it is necessary to satisfy that the pipeline resistance in the first cooling channel is less than the driving force generated by the thermosyphon effect; for example, when the vertical distance ≥ 2 meters and the horizontal distance ≤ 2 meters, the thermosyphon demand of R134a refrigerant can be satisfied.

[0033] Taking the magnetic levitation refrigeration compressor 1 of 200RT (refrigerating capacity of 200 refrigeration tons) as an example below, the design principle of cooling the motor by using the thermosyphon effect is described in detail through theoretical calculations.

[0034] Theoretical explanation: The thermosyphon effect uses the density difference (Δρ) and height difference (ΔH) of the refrigerant in the pipeline between the thermosyphon tank 5 and the magnetic levitation refrigeration compressor 1 to generate a static pressure head to drive the refrigerant circulation, and the static pressure head needs to be greater than the total pressure drop of the pipeline. The circulation ratio is defined as the ratio of the total mass flow rate of the circulating refrigerant to the evaporation rate, and it is necessary to ensure a sufficient ratio to avoid dry-out. The circulation ratio is generally set between 3 and 6.

[0035] 1. Calculation of initial conditions: The magnetic levitation refrigeration compressor 1 of 200RT, with a motor power of 120KW, a motor efficiency of 97%, a motor heat generation of 3.6KW, and a motor cooling annular flow channel is provided inside the magnetic levitation refrigeration compressor 1. The vertical distance ΔH between the thermosyphon tank 5 and the magnetic levitation refrigeration compressor 1 is 2m, and the horizontal distance is 1.5m. The condensation temperature of the evaporative condenser 2 is 36°C, the subcooling degree is 2°C, the temperature of the refrigerant in the thermosyphon tank 5 is 34°C, and the density ρ_ L of the liquid refrigerant R134a (abbreviation of 1,1,1,2-tetrafluoroethane) in the first liquid discharge pipe 6 is 1171 kg / m³, and the density ρ_ v of the gaseous refrigerant R134a in the first return pipe 7 is 42 kg / m³, and the circulation ratio is set to 3.

[0036] 2. Driving force calculation: ΔP = [ρ_ L − (1 / 3 * ρ_ v+2 / 3*ρ_ L *g*ΔH = 7400 Pa; Wherein, g is the acceleration due to gravity, with a value of 9.81. Substituting the values, we get: ΔP = 7.4 kPa.

[0037] Pipeline design and pressure drop calculation: The pressure drop includes pipeline friction pressure drop and local pressure drop. The first liquid outlet pipe 6 between the thermosyphon tank 5 and the magnetic levitation refrigeration compressor 1 uses a copper pipe with a diameter of 16 mm, and the first return pipe 7 selects a copper pipe with a diameter of 28 mm. There are 3 90-degree elbows on the first liquid outlet pipe 6 and the first return pipe 7 respectively. The pipe diameters of the first liquid outlet pipe 6 and the first return pipe 7 are reasonably designed to reduce the pipeline resistance during the refrigerant flow.

[0038] Pipeline friction pressure drop (Darcy formula): ΔP f = f * L / D * (ρ * u 2 / 2); Local pressure drop (elbow): ΔP l = ξ * (ρ * u 2 / 2); In the formula, f is the friction factor, L is the pipe length, D is the pipe diameter, u is the flow velocity, and ξ is the local resistance coefficient.

[0039] Calculation results: The pressure drop ΔP of the internal motor cooling annular flow channel of the magnetic levitation refrigeration compressor 1 n = 3600 Pa; The pipeline friction pressure drop ΔP f = 800 Pa; The local pressure drop ΔP l = 400 Pa; The total pressure drop ΔP t = 4800 Pa.

[0040] The driving force ΔP = 7400 Pa > the total pressure drop ΔP t = 4800 Pa. The theoretical calculation of the design scheme is valid. The pipeline resistance is less than the driving force generated by the thermosyphon effect, and it can meet the circulation conditions of the first cooling channel.

[0041] Example 8 For the magnetic levitation centrifugal chiller based on thermosyphon cooling provided in any one of Examples 4 - 7, this example provides a corresponding control method, including: Connect the first cooling channel and start the magnetic levitation refrigeration compressor 1. Under the thermosyphon effect, the liquid refrigerant flowing out of the thermosyphon tank 5 absorbs the heat of the magnetic levitation refrigeration compressor 1 and vaporizes to form a gas-liquid mixture, and then returns to the thermosyphon tank 5, circulating between the magnetic levitation refrigeration compressor 1 and the thermosyphon tank 5 to achieve the cooling of the magnetic levitation refrigeration compressor 1; Under the pressure difference between the thermosyphon tank 5 and the evaporative condenser 2, the gaseous refrigerant flowing back into the thermosyphon tank 5 enters the evaporative condenser 2 and condenses into liquid refrigerant, and then the liquid refrigerant is transported to the thermosyphon tank 5; When the liquid refrigerant level in the thermosyphon tank 5 exceeds the set value, the liquid refrigerant is transported to the liquid receiver 3 through the liquid return pipe 12 to continue the main refrigeration cycle of the magnetic levitation centrifugal chiller.

[0042] Embodiment 9 This embodiment provides a control method for a magnetic levitation centrifugal chiller, which is different from Embodiment 8 in that: An electromagnetic valve 13 is further provided on the second liquid outlet pipe 8, and the control method further includes: The motor temperature T of the magnetic levitation refrigeration compressor 1 is monitored in real time. The motor temperature T takes the highest value detected inside the motor as the motor temperature T. Temperature sensors can be arranged at the motor winding, rotor and bearing, and the highest value is taken as T; when T≥the first set threshold T1, the electromagnetic valve 13 and the second expansion valve 17 on the second liquid outlet pipe 8 are opened to connect the second cooling channel; the liquid refrigerant in the liquid receiver 3 enters the magnetic levitation refrigeration compressor 1 through the second liquid outlet pipe 8, evaporates into gaseous refrigerant after absorbing heat, and returns to the evaporator 4 through the second return pipe 9; the second expansion valve 17 on the second liquid outlet pipe 8 adjusts the refrigerant flow rate to match the compressor heat dissipation requirement.

[0043] When T<T2 and T2<T1, the electromagnetic valve 13 and the second expansion valve 17 on the second liquid outlet pipe 8 are closed, and the second cooling channel stops operating. T2 represents the second set threshold, which is set based on the lower temperature limit for the stable operation of the magnetic levitation centrifugal chiller. Setting the second set threshold T2 can prevent the electromagnetic valve 13 from starting and stopping frequently.

[0044] Utilizing the thermosyphon effect to cool the magnetic levitation refrigeration compressor 1 is limited by the relationship between pipeline resistance and gravitational potential energy. When the installation height of the thermosyphon tank 5 is insufficient due to site conditions, the cooling effect of the first cooling channel weakens, which may cause the temperature of the magnetic levitation refrigeration compressor 1 to be too high; when the magnetic levitation refrigeration compressor 1 operates under extreme conditions or at high loads, the heat generation may exceed the upper limit of the cooling capacity of the thermosyphon effect. Therefore, to ensure the safe and efficient operation of the magnetic levitation refrigeration compressor 1 under various conditions, when the motor heat generation exceeds the maximum heat exchange capacity of the first cooling channel and the temperature of the magnetic levitation refrigeration compressor 1 continues to rise, it is necessary to control the refrigerant to enter the second cooling channel to assist in cooling.

[0045] The foregoing description has shown and described the preferred embodiments of the present application. However, as mentioned before, it should be understood that the present application is not limited to the forms disclosed herein, and should not be regarded as excluding other embodiments. Instead, it can be used in various other combinations, modifications, and environments, and can be changed within the scope conceived herein through the above teachings or the techniques or knowledge in the relevant field. Any changes and variations made by those skilled in the art without departing from the spirit and scope of the present application shall fall within the protection scope of the appended claims of the present application.

Claims

1. A magnetic levitation centrifugal chiller based on thermosyphon cooling, characterized in that, It includes a magnetic levitation refrigeration compressor, an evaporative condenser, a thermosyphon tank, a liquid receiver, a first expansion valve and an evaporator which are connected in sequence; In the main refrigeration cycle of the magnetic levitation centrifugal chiller, the gaseous refrigerant output from the evaporator is compressed by the magnetic levitation refrigeration compressor and condensed by the evaporative condenser to become a liquid refrigerant. The liquid refrigerant then flows from the evaporative condenser into the thermosyphon tank. When the liquid refrigerant in the thermosyphon tank exceeds the set liquid level, the liquid refrigerant flows through the liquid receiver, the first expansion valve and the evaporator in sequence, and circulates repeatedly to complete the main refrigeration cycle of the magnetic levitation centrifugal chiller; A first cooling channel is also provided between the thermosyphon tank and the magnetic levitation refrigeration compressor. By using the thermosyphon effect, the refrigerant in the magnetic levitation refrigeration compressor circulates between the thermosyphon tank and the magnetic levitation refrigeration compressor to achieve the cooling of the magnetic levitation refrigeration compressor.

2. The magnetic levitation centrifugal chiller based on thermosyphon cooling according to claim 1, wherein, A first liquid outlet pipe and a first return pipe are respectively provided between the thermosyphon tank and the magnetic levitation refrigeration compressor. The first liquid outlet pipe and the first return pipe are respectively connected to the inlet and the outlet of the first refrigerant channel in the magnetic levitation refrigeration compressor. The thermosyphon tank, the first liquid outlet pipe, the magnetic levitation refrigeration compressor and the first return pipe are connected to form a first cooling channel.

3. The magnetic levitation centrifugal chiller based on thermosyphon cooling according to claim 2, wherein A first liquid inlet pipe is provided between the evaporative condenser and the thermosyphon tank, an exhaust pipe is provided between the magnetic levitation refrigeration compressor and the evaporative condenser, and the thermosyphon tank is also connected to the exhaust pipe through an exhaust bypass pipe.

4. The magnetic levitation centrifugal chiller based on thermosyphon cooling according to claim 2, wherein The magnetic levitation centrifugal chiller is also provided with a second cooling channel. A second liquid outlet pipe is provided between the liquid receiver and the magnetic levitation refrigeration compressor. A solenoid valve and a second expansion valve are provided on the second liquid outlet pipe. A second return pipe is provided between the magnetic levitation refrigeration compressor and the evaporator. And the second liquid outlet pipe and the second return pipe are respectively connected to the inlet and the outlet of the second refrigerant channel in the magnetic levitation refrigeration compressor. The liquid receiver, the second liquid outlet pipe, the magnetic levitation refrigeration compressor, the second return pipe and the evaporator form a second cooling channel.

5. The magnetic levitation centrifugal chiller based on thermosyphon cooling according to claim 4, wherein A drain pipe is provided between the thermosyphon tank and the liquid receiver; a liquid return pipe is provided between the liquid receiver and the evaporator, and the first expansion valve is provided on the liquid return pipe.

6. The magnetic levitation centrifugal chiller based on thermosyphon cooling according to claim 4, wherein, The installation position of the evaporative condenser needs to be higher than that of the thermosyphon tank, and the installation position of the thermosyphon tank is higher than that of the liquid receiver.

7. The magnetic levitation centrifugal chiller based on thermosyphon cooling according to claim 4, wherein The installation position of the thermosyphon tank is higher than that of the magnetic levitation refrigeration compressor, and it satisfies that the pipeline resistance in the first cooling channel is less than the driving force generated by the thermosyphon effect.

8. The control method of the magnetic levitation centrifugal chiller according to any one of claims 4-7, characterized in that, It includes: Connect the first cooling channel, start the magnetic levitation refrigeration compressor. Under the thermosyphon effect, the liquid refrigerant flowing out of the thermosyphon tank absorbs the heat of the magnetic levitation refrigeration compressor and vaporizes to form a gas-liquid mixture state, and then flows back to the thermosyphon tank, circulating between the magnetic levitation refrigeration compressor and the thermosyphon tank to achieve the cooling of the magnetic levitation refrigeration compressor; The gaseous refrigerant flowing back into the thermosyphon tank enters the evaporative condenser under the action of the pressure difference and condenses into a liquid refrigerant. The liquid refrigerant in the evaporative condenser is transported back to the thermosyphon tank again under the action of gravity; When the liquid refrigerant level in the thermosyphon tank exceeds the set height, the liquid refrigerant is transported to the liquid receiver to continue the main refrigeration cycle of the magnetic levitation centrifugal chiller.

9. The control method of the magnetic levitation centrifugal chiller according to claim 8, wherein, A solenoid valve is also provided on the second liquid outlet pipe, and the control method further includes: Real-time monitoring of the motor temperature T of the magnetic levitation refrigeration compressor, when T≥the first set threshold T1, opening the solenoid valve and the expansion valve on the second liquid outlet pipe to connect the second cooling channel; When T<T2 and T2<T1, closing the solenoid valve and the expansion valve on the second liquid outlet pipe, and the second cooling channel stops operating. T2 represents the second set threshold, which is set based on the lower temperature limit for the stable operation of the magnetic levitation centrifugal chiller.

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