Magnetic levitation water chiller and control method

Abstract

The present application relates to a kind of magnetic levitation water chiller unit and control method, belong to magnetic levitation refrigeration technical field.Unit includes magnetic levitation compressor, condenser, gas-liquid separator and thermosyphon evaporator, condenser is higher than gas-liquid separator and main liquid supply pipe has no liquid supply driven pump.Control method according to the temperature difference of outdoor temperature and water supply temperature automatically switches three kinds of operating mode: high temperature season with compression refrigeration operation;Transition season according to the opening of main electronic expansion valve to the opening control of auxiliary electronic expansion valve;Low temperature season switches to heat pipe natural cooling, through first adjusting fan or water pump, then gradually opening branch to carry out cold quantity regulation.The present application realizes high efficiency operation in all working conditions, and reduces operating energy consumption.

Description

Technical Field

[0001] This invention relates to a magnetic levitation chiller unit and its control method, belonging to the field of magnetic levitation refrigeration technology. Background Technology

[0002] In the context of continuously upgrading energy efficiency requirements for refrigeration systems, the rational use of natural cold sources is crucial for reducing system energy consumption. Currently, the main operating modes of the heat pipe coupled magnetic levitation chiller composite refrigeration system are as follows: During the high-temperature season, the magnetic levitation chiller unit provides independent refrigeration, with direct expansion supplying liquid to cool the evaporator; during the transitional season, as the outdoor ambient temperature gradually decreases, the unit's operating pressure ratio drops significantly, requiring a refrigerant pump to force refrigerant to be delivered to the evaporator; during the low-temperature season, the chiller unit is shut down, relying entirely on the heat pipe to extract outdoor natural cold sources, again relying on a refrigerant pump to complete the refrigerant circulation.

[0003] First, existing hybrid refrigeration systems use refrigerant pumps to deliver refrigerant during transitional and cold seasons, which generates additional power consumption. Second, when obtaining natural cooling sources during cold seasons, existing heat pipe systems adjust the cooling load solely by regulating the frequency of the outdoor condenser fan or spray pump, resulting in a narrow adjustment range and poor temperature control stability. Especially in cold regions, even with the condenser fan and spray pump completely shut off, natural air convection can still lead to excessive cooling output from the heat pipes, causing the evaporator to operate at excessively low temperatures and even posing a safety risk of pipe freezing. Furthermore, during the transition from hot to transitional seasons, the unit's operating pressure ratio decreases significantly, and the pressure differential of the magnetic levitation motor cooling system decreases significantly. Existing technologies lack a design for a magnetic levitation motor cooling solution specifically for hybrid refrigeration systems. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a magnetic levitation chiller unit that employs a thermosiphon evaporator. A main electronic expansion valve is installed on the main liquid supply pipe, with auxiliary electric expansion valves connected in parallel across its two ends. These auxiliary electric expansion valves ensure sufficient refrigerant supply to the evaporator under low pressure ratio or gravity-fed conditions, eliminating the need for a refrigerant delivery pump. Furthermore, the outdoor condenser's main intake pipe is branched into multiple parallel branches, each containing multiple sets of condensing coils and equipped with an on / off valve. This broadens the cooling capacity adjustment range of the heat pipe system and effectively mitigates equipment risks caused by excessively low evaporation temperatures during natural cooling circulation in low-temperature environments.

[0005] The present invention also provides a control method for the above-mentioned magnetic levitation chiller unit.

[0006] The technical solution of this invention is as follows: A magnetic levitation chiller unit includes a magnetic levitation refrigeration compressor, a condenser, a gas-liquid separator, and a thermosiphon evaporator. The refrigerant outlet of the condenser is connected to the liquid inlet of the gas-liquid separator via a main liquid supply pipe. The liquid outlet of the gas-liquid separator is connected to the liquid inlet of the thermosiphon evaporator via an evaporator liquid inlet pipe. The gas outlet of the thermosiphon evaporator is connected to the gas return port of the gas-liquid separator via an evaporator gas return pipe. The gas outlet of the gas-liquid separator is connected to the suction port of the magnetic levitation refrigeration compressor via a gas supply pipe. The gas outlet of the magnetic levitation refrigeration compressor is connected to the refrigerant inlet of the condenser via an exhaust pipe. The exhaust pipe and the gas supply pipe are connected by a first connecting pipe. A main electronic expansion valve is installed on the main liquid supply pipe, and auxiliary electric expansion valves are connected in parallel at both ends of the main electronic expansion valve. No liquid refrigerant pump is installed on the main liquid supply pipe. The vertical installation height of the condenser is higher than that of the gas-liquid separator. The liquid refrigerant flows from the condenser to the gas-liquid separator through the main liquid supply pipe, relying on the pressure generated by the unit pressure difference and / or the vertical installation height difference between the condenser and the gas-liquid separator.

[0007] According to a preferred embodiment of the present invention, a cooling supply branch pipe is also provided on the main liquid supply pipe. The cooling supply branch pipe is connected to the motor cooling inlet of the magnetic levitation refrigeration compressor. The motor cooling outlet of the magnetic levitation refrigeration compressor is connected to the gas-liquid separator through a cooling return pipe. A one-way valve and an auxiliary refrigerant pump are provided on the cooling supply branch pipe. The auxiliary refrigerant pump is connected in parallel with the one-way valve. The conduction direction of the one-way valve is from the main liquid supply pipe to the motor cooling inlet.

[0008] According to a preferred embodiment of the present invention, the condenser includes a condensing coil, a fan and / or a spray water pump. The air inlet side of the condenser is provided with several parallel branches, each branch is provided with several sets of condensing coils, and each branch is also provided with a switch valve.

[0009] The above-mentioned control method for a magnetic levitation chiller unit, applied to the aforementioned magnetic levitation chiller unit, includes: The operating mode is executed according to the temperature difference between the outdoor ambient temperature and the user's water supply temperature, i.e., temperature difference = outdoor ambient temperature - user's water supply temperature. When the temperature difference is greater than or equal to the first temperature threshold, the high-temperature season operation mode is executed. When the temperature difference is less than the first temperature threshold and the temperature difference is greater than or equal to the second temperature threshold, the transitional season operation mode is executed. When the temperature difference is less than the second temperature threshold, the low-temperature seasonal operation mode is executed. Wherein, the first temperature threshold is greater than the second temperature threshold. During the high-temperature season and transitional season, it operates in compression refrigeration cycle mode, while during the low-temperature season, it switches to heat pipe natural cooling cycle mode.

[0010] According to a preferred embodiment of the present invention, the high-temperature season operation mode includes: Turn on the magnetic levitation refrigeration compressor, open the first valve on the gas supply pipe, close the second valve on the first connecting pipe, and the gaseous refrigerant output from the gas-liquid separator enters the magnetic levitation refrigeration compressor through the gas supply pipe for compression, and then is delivered to the air inlet of the condenser through the exhaust pipe for compression refrigeration cycle. Specifically, the main electronic expansion valve on the main liquid supply pipe is opened, and the auxiliary electric expansion valve is closed; the liquid refrigerant is transported from the condenser to the gas-liquid separator through the main liquid supply pipe under the pressure difference drive; In a further preferred embodiment, during the high-temperature season operation mode, the auxiliary refrigerant pump is turned off, and the liquid refrigerant is delivered to the motor cooling inlet by the cooling liquid supply branch pipe under the pressure difference drive; the switching valves on all branches in the condenser are opened.

[0011] According to a preferred embodiment of the present invention, the transitional season operation mode includes: Turn on the magnetic levitation refrigeration compressor, open the first valve on the gas supply pipe, close the second valve on the first connecting pipe, and the gaseous refrigerant output from the gas-liquid separator enters the magnetic levitation refrigeration compressor through the gas supply pipe for compression, and then is delivered to the air inlet of the condenser through the exhaust pipe for compression refrigeration cycle. Among them, the main electronic expansion valve on the main liquid supply pipe is opened; the liquid refrigerant is driven by the pressure difference and uses the pressure generated by the vertical installation height difference between the condenser and the gas-liquid separator to be transported from the condenser to the gas-liquid separator through the main liquid supply pipe. The opening signal of the main electronic expansion valve is collected in real time. When the opening of the main electronic expansion valve reaches the set opening threshold, the auxiliary electric expansion valve is opened. Based on the opening signal of the main electronic expansion valve, the opening of the auxiliary electric expansion valve is controlled in stages. In a further preferred embodiment, during the transitional season operation mode, when the unit's operating pressure ratio drops to the minimum pressure ratio threshold required for cooling the magnetic levitation refrigeration compressor, the auxiliary refrigerant pump on the cooling liquid supply branch pipe is turned on to deliver liquid refrigerant to the motor cooling inlet of the magnetic levitation refrigeration compressor.

[0012] According to a preferred embodiment of the present invention, the step of performing graded opening control of the auxiliary electric expansion valve based on the opening signal of the main electronic expansion valve includes: When the opening degree of the main electronic expansion valve reaches the fourth opening degree threshold, the auxiliary electric expansion valve is controlled to open to the first opening degree position. When the opening degree of the main electronic expansion valve reaches the third opening degree threshold, the auxiliary electric expansion valve is controlled to open to the second opening degree position. When the opening degree of the main electronic expansion valve reaches the second opening degree threshold, the auxiliary electric expansion valve is controlled to open to the third opening degree position. When the opening degree of the main electronic expansion valve reaches the first opening degree threshold, the auxiliary electric expansion valve is controlled to open to the fourth opening degree position.

[0013] Among them, the fourth opening threshold < the third opening threshold < the second opening threshold < the first opening threshold, and the fourth opening level > the third opening level > the second opening level > the first opening level.

[0014] According to a preferred embodiment of the present invention, the graded opening control further includes downshift control: When the auxiliary electric expansion valve is in the open state, when the opening degree of the main electronic expansion valve drops to the fifth opening degree threshold, the opening degree of the auxiliary electric expansion valve decreases by one level. When the opening degree of the main electronic expansion valve drops to the sixth opening degree threshold, the opening degree of the auxiliary electric expansion valve decreases by 2 levels. When the opening degree of the main electronic expansion valve drops to the seventh opening degree threshold, the opening degree of the auxiliary electric expansion valve decreases by 3 levels. When the opening degree of the main electronic expansion valve drops to the eighth opening degree threshold, the opening degree of the auxiliary electric expansion valve decreases by 4 levels, that is, the auxiliary electric expansion valve is closed. Among them, the fourth opening threshold > the fifth opening threshold > the sixth opening threshold > the seventh opening threshold > the eighth opening threshold.

[0015] According to a preferred embodiment of the present invention, the low-temperature seasonal operation mode includes: Turn off the magnetic levitation refrigeration compressor, close the first valve on the gas supply pipe, open the second valve on the first connecting pipe, and the gaseous refrigerant output from the gas-liquid separator is transported to the gas inlet of the condenser through the gas supply pipe, the first connecting pipe, and the exhaust pipe. The liquid refrigerant is supplied by gravity between the condenser and the thermosiphon evaporator, and the natural cooling capacity extracted by the heat pipe natural cooling circuit is transported to the thermosiphon evaporator. The main electronic expansion valve and auxiliary electric expansion valve on the main liquid supply pipe are fully open to reduce the flow resistance of the pipeline. The liquid refrigerant is transported from the condenser to the gas-liquid separator by means of the pressure generated by the vertical installation height difference between the condenser and the gas-liquid separator.

[0016] According to a preferred embodiment of the present invention, in the low-temperature seasonal operation mode, the cooling capacity adjustment of the heat pipe natural cooling circuit includes: When the refrigerant evaporation temperature is within the preset temperature range, the cooling capacity is adjusted only by regulating the operating frequency of the condenser fan and / or spray water pump. When both the fan and the spray pump have been reduced to the minimum allowable operating frequency, and the refrigerant evaporation temperature is still below the lower limit of the preset temperature range, turn off the fan and the spray pump of the condenser to reduce the cooling capacity. When the fan and spray pump are both turned off, and the refrigerant evaporation temperature is still lower than the lower limit of the preset temperature range, the switching valves on some branches are closed one by one to reduce the condensing heat exchange area and further reduce the cooling capacity until the refrigerant evaporation temperature rises back to the preset temperature range, and the condenser fan and pump resume the frequency conversion regulation mode. When the fan and spray pump have both increased to the maximum allowable operating frequency and the refrigerant evaporation temperature is still higher than the preset upper limit of temperature, the switch valves on the closed branches are opened one by one to increase the condensing heat exchange area and increase the cooling capacity until the refrigerant evaporation temperature drops back to the preset temperature range.

[0017] The beneficial effects of this invention are as follows: 1. This invention provides a magnetic levitation chiller unit, which adopts a thermosiphon evaporator and is equipped with a corresponding system structure and control scheme, completely eliminating the extra power consumption of the fluorine pump during the transition season and low temperature season, and improving the overall energy efficiency of the system.

[0018] 2. A parallel branch of an electric expansion valve is added to the main refrigerant supply pipe to reduce pipeline resistance under gravity supply and low-pressure-ratio supply conditions, ensuring a sufficient and stable refrigerant supply. The main electronic expansion valve works in conjunction with the auxiliary electric expansion valve. During high-temperature seasons, the main electronic expansion valve independently throttles the refrigerant supply; during transitional seasons, when the main electronic expansion valve's supply is insufficient, the auxiliary electric expansion valve opens in stages to supplement the supply; during low-temperature seasons, both the main electronic expansion valve and the auxiliary electric expansion valve are fully open to reduce pipeline resistance and ensure a sufficient gravity refrigerant supply.

[0019] 3. The condenser intake manifold is divided into multiple parallel branches, each with an independent on / off valve. The effective heat exchange area of ​​the condenser can be adjusted by switching the valves on and off, thus expanding the cooling capacity adjustment range of the heat pipe natural cooling circuit. This solves the problem of excessive cooling capacity in heat pipe systems in cold regions, effectively avoids the risk of excessively low evaporation temperature and freezing of evaporator pipes, and improves the system's temperature control accuracy and adaptability to low-temperature environments.

[0020] 4. An auxiliary refrigerant pump is added to the motor cooling pipeline of the magnetic levitation refrigeration compressor. This pump can actively increase pressure and replenish flow when the system pressure ratio decreases or the cooling supply pressure differential weakens during the transition season. This prevents the motor from overheating and experiencing performance degradation due to insufficient cooling, thereby improving the stability and reliability of the unit's operation. Attached Figure Description

[0021] Figure 1 This is a structural schematic diagram of a magnetic levitation chiller unit provided by the present invention.

[0022] Figure 2 This is a schematic diagram of a control method for a magnetic levitation chiller unit provided by the present invention.

[0023] 1. Magnetic levitation refrigeration compressor; 2. Condenser; 3. Gas-liquid separator; 4. Thermosiphon evaporator; 5. Main liquid supply pipe; 6. Evaporator liquid inlet pipe; 7. Evaporator gas return pipe; 8. Gas supply pipe; 9. Cooling liquid supply branch pipe; 10. Cooling gas return pipe; 11. Main electronic expansion valve; 12. Auxiliary electric expansion valve; 13. Check valve; 14. Auxiliary refrigerant pump; 15. Switch valve; 16. Exhaust pipe; 17. First connecting pipe; 18. Branch line; 19. First valve; 20. Second valve. Detailed Implementation

[0024] 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.

[0025] This invention provides a magnetic levitation chiller unit, such as... Figure 1 As shown, it includes a magnetic levitation refrigeration compressor 1, a condenser 2, a gas-liquid separator 3, and a thermosiphon evaporator 4. The refrigerant outlet of condenser 2 is connected to the liquid inlet of gas-liquid separator 3 via main liquid supply pipe 5. The liquid outlet of gas-liquid separator 3 is connected to the liquid inlet of thermosiphon evaporator 4 via evaporator liquid inlet pipe 6. The gas outlet of thermosiphon evaporator 4 is connected to the gas return port of gas-liquid separator 3 via evaporator gas return pipe 7. The gas outlet of gas-liquid separator 3 is connected to the suction port of magnetic levitation compressor 1 via gas supply pipe 8. The gas outlet of magnetic levitation compressor 1 is connected to the refrigerant inlet of condenser 2 via exhaust pipe 16. The exhaust pipe 16 and the gas supply pipe 8 are connected via a first connecting pipe 17. A main electronic expansion valve 11 is installed on the main liquid supply pipe 5, and an auxiliary electric expansion valve 12 is connected in parallel at both ends of the main electronic expansion valve 11. No liquid refrigerant pump is installed on the main liquid supply pipe 5. The vertical installation height of the condenser 2 is higher than the vertical installation height of the gas-liquid separator 3. The liquid refrigerant flows from the condenser 2 to the gas-liquid separator 3 through the main liquid supply pipe 5, relying on the pressure generated by the unit pressure difference and / or the vertical installation height difference between the condenser 2 and the gas-liquid separator 3.

[0026] In one embodiment, a cooling supply branch pipe 9 is also provided on the main liquid supply pipe 5. The cooling supply branch pipe 9 is connected to the motor cooling inlet of the magnetic levitation refrigeration compressor 1. The motor cooling outlet of the magnetic levitation refrigeration compressor 1 is connected to the gas-liquid separator 3 through the cooling return pipe 10. A one-way valve 13 and an auxiliary refrigerant pump 14 are provided on the cooling supply branch pipe 9. The auxiliary refrigerant pump 14 is connected in parallel with the one-way valve 13. The conduction direction of the one-way valve 13 is from the main liquid supply pipe 5 to the motor cooling inlet.

[0027] An auxiliary refrigerant pump 14 is installed on the cooling liquid supply branch pipe 9 of the magnetic levitation refrigeration compressor 1. When the unit's pressure ratio is low and the cooling liquid supply pressure difference is insufficient during the transition season, the refrigerant pump delivers refrigerant to dissipate heat from the motor, preventing the motor from overheating and being damaged, and ensuring the safe operation of the unit.

[0028] In one embodiment, the condenser 2 includes a condensing coil, a fan, and / or a spray water pump. The condenser 2 can be an air-cooled condenser 2 or an evaporative condenser 2. When the condenser 2 is an air-cooled condenser 2, it includes a condensing coil and a fan; when the condenser 2 is an evaporative condenser 2, it includes a condensing coil, a fan, and a spray water pump. The condenser 2 has several parallel branches 18 on its air inlet side. Each branch 18 has several sets of condensing coils and a switch valve 15 on each branch 18.

[0029] When using a heat pipe natural cooling circulation loop to obtain natural cold source in cold regions, if the output of the heat pipe system is still too large after completely shutting off the condenser 2 fan and / or spray water pump, the effective heat exchange area of ​​the condenser coil can be reduced by closing the switch valve 15 of branch 18, thereby further reducing the output of the heat pipe system, expanding the range of cold capacity adjustment, and avoiding various equipment hazards caused by excessive cold capacity in cold regions.

[0030] Embodiments of the present invention also provide a control method for a magnetic levitation chiller unit, such as... Figure 2 As shown, the magnetic levitation chiller unit described above includes: The corresponding operating mode is executed based on the temperature difference ΔT between the outdoor ambient temperature and the user's water supply temperature, i.e., temperature difference ΔT = outdoor ambient temperature - user's water supply temperature. When the temperature difference is greater than or equal to the first temperature threshold, the high-temperature season operation mode is executed. When the temperature difference is less than the first temperature threshold and the temperature difference is greater than or equal to the second temperature threshold, the transitional season operation mode is executed. When the temperature difference is less than the second temperature threshold, the low-temperature seasonal operation mode is executed. Wherein, the first temperature threshold is greater than the second temperature threshold. During the high-temperature season and transitional season, it operates in compression refrigeration cycle mode, while during the low-temperature season, it switches to heat pipe natural cooling cycle mode.

[0031] In one embodiment, the high-temperature season operation mode includes: Turn on the magnetic levitation refrigeration compressor 1, open the first valve 19 on the gas supply pipe 8, and close the second valve 20 on the first connecting pipe 17. The gaseous refrigerant output from the gas-liquid separator 3 enters the magnetic levitation refrigeration compressor 1 through the gas supply pipe 8 for compression, and then is delivered to the air inlet of the condenser 2 through the exhaust pipe 16 for compression refrigeration cycle. Specifically, the refrigerant is compressed by the magnetic levitation refrigeration compressor 1 and enters the condenser 2 through the exhaust pipe 16 for condensation. The liquid refrigerant output from the condenser 2 is throttled by the main electronic expansion valve 11, evaporated by the thermosiphon evaporator 4, and separated by the gas-liquid separator 3. Then it returns to the magnetic levitation refrigeration compressor 1 through the gas supply pipe 8 to realize the compression refrigeration cycle. Among them, the main electronic expansion valve 11 on the main liquid supply pipe 5 is opened, and the auxiliary electric expansion valve 12 is closed; the liquid refrigerant is transported from the condenser 2 to the gas-liquid separator 3 through the main liquid supply pipe 5 under the pressure difference drive. In one embodiment, during the high-temperature season operation mode, the auxiliary refrigerant pump 14 is turned off, and the liquid refrigerant is delivered to the motor cooling inlet of the magnetic levitation refrigeration compressor by the cooling liquid supply branch pipe 9 under the pressure difference drive; the switching valves 15 on all branches 18 in the condenser 2 are turned on.

[0032] In one embodiment, the transitional season operation mode includes: Turn on the magnetic levitation refrigeration compressor 1, open the first valve 19 on the gas supply pipe 8, and close the second valve 20 on the first connecting pipe 17. The gaseous refrigerant output from the gas-liquid separator 3 enters the magnetic levitation refrigeration compressor 1 through the gas supply pipe 8 for compression, and then is delivered to the air inlet of the condenser 2 through the exhaust pipe 16 for compression refrigeration cycle. Specifically, the refrigerant is compressed by the magnetic levitation refrigeration compressor 1 and enters the condenser 2 through the exhaust pipe 16 for condensation. The liquid refrigerant output from the condenser 2 is throttled by the main electronic expansion valve 11, evaporated by the thermosiphon evaporator 4, and separated by the gas-liquid separator 3. Then it returns to the magnetic levitation refrigeration compressor 1 through the gas supply pipe 8 to realize the compression refrigeration cycle. Among them, the main electronic expansion valve 11 on the main liquid supply pipe 5 is opened; the liquid refrigerant is driven by the pressure difference and uses the pressure generated by the vertical installation height difference between the condenser 2 and the gas-liquid separator 3 to be transported from the condenser 2 to the gas-liquid separator 3 through the main liquid supply pipe 5. The opening signal of the main electronic expansion valve 11 is collected in real time. When the opening of the main electronic expansion valve 11 reaches the set opening threshold, the auxiliary electric expansion valve 12 is opened. Based on the opening signal of the main electronic expansion valve 11, the opening of the auxiliary electric expansion valve 12 is controlled in stages.

[0033] In one embodiment, during the transitional season operation mode, when the unit operating pressure ratio drops to the minimum pressure ratio threshold required for cooling the magnetic levitation refrigeration compressor 1, the auxiliary refrigerant pump 14 on the cooling liquid supply branch pipe 9 is turned on to deliver liquid refrigerant to the motor cooling inlet of the magnetic levitation refrigeration compressor 1.

[0034] Although the system continues to operate in compression refrigeration mode during the transitional season, the decrease in outdoor ambient temperature leads to a drop in condensing pressure and a reduction in system pressure differential, resulting in insufficient driving force for the main circulation liquid supply. This invention addresses this by employing graded opening control. Based on the opening signal of the main electronic expansion valve 11, the auxiliary electric expansion valve 12 is set to multiple opening levels (e.g., 25%, 50%, 75%, 100%), achieving step-by-step and precise compensation for the liquid supply flow. Compared to traditional single-opening control or full-open / full-close control, this method can match the appropriate compensation amount according to the degree of insufficient liquid supply, ensuring stable liquid level in the gas-liquid separator 3. Simultaneously, by setting up and down thresholds, frequent valve position movements near the thresholds are effectively prevented, improving the stability and reliability of the control.

[0035] In one embodiment, based on the opening signal of the main electronic expansion valve 11, the auxiliary electric expansion valve 12 is subjected to graded opening control, including: When the opening degree of the main electronic expansion valve 11 reaches the fourth opening degree threshold, the auxiliary electric expansion valve 12 is controlled to open to the first opening degree position. When the opening degree of the main electronic expansion valve 11 reaches the third opening degree threshold, the auxiliary electric expansion valve 12 is controlled to open to the second opening degree position. When the opening degree of the main electronic expansion valve 11 reaches the second opening degree threshold, the auxiliary electric expansion valve 12 is controlled to open to the third opening degree position. When the opening degree of the main electronic expansion valve 11 reaches the first opening degree threshold, the auxiliary electric expansion valve 12 is controlled to open to the fourth opening degree position.

[0036] Among them, the fourth opening threshold < the third opening threshold < the second opening threshold < the first opening threshold, and the fourth opening level > the third opening level > the second opening level > the first opening level.

[0037] In one embodiment, the graded opening control further includes downshift control: When the auxiliary electric expansion valve 12 is in the open state, when the opening degree of the main electronic expansion valve 11 drops to the fifth opening degree threshold, the opening degree of the auxiliary electric expansion valve 12 decreases by one level. When the opening degree of the main electronic expansion valve 11 drops to the sixth opening degree threshold, the opening degree of the auxiliary electric expansion valve 12 decreases by 2 levels. When the opening degree of the main electronic expansion valve 11 drops to the seventh opening degree threshold, the opening degree of the auxiliary electric expansion valve 12 decreases by 3 levels. When the opening degree of the main electronic expansion valve 11 drops to the eighth opening degree threshold, the opening degree of the auxiliary electric expansion valve 12 decreases by 4 levels, that is, the auxiliary electric expansion valve 12 is closed. Among them, the fourth opening threshold > the fifth opening threshold > the sixth opening threshold > the seventh opening threshold > the eighth opening threshold.

[0038] Specifically, the fourth threshold is 80%, the third threshold is 85%, the second threshold is 90%, and the first threshold is 95%. The first opening setting is 25%, the second opening setting is 50%, the third opening setting is 75%, and the fourth opening setting is 100%. The threshold for the fifth opening degree is 40%, the threshold for the sixth opening degree is 35%, the threshold for the seventh opening degree is 30%, and the threshold for the eighth opening degree is 25%.

[0039] In addition, in the graded opening control, when the opening of the main electronic expansion valve 11 reaches each opening threshold and runs continuously for a preset time, the corresponding opening adjustment action of the auxiliary electric expansion valve 12 is then executed.

[0040] Specifically, when the main electronic expansion valve 11 is open ≥80% and has been running continuously for more than 30 seconds, the auxiliary electric expansion valve 12 is controlled to open to a fixed 25% opening; when the main electronic expansion valve 11 is open ≥85% and has been running continuously for more than 30 seconds, the auxiliary electric expansion valve 12 is controlled to open to a fixed 50% opening; when the main electronic expansion valve 11 is open ≥90% and has been running continuously for more than 30 seconds, the auxiliary electric expansion valve 12 is controlled to open to a fixed 75% opening; when the main electronic expansion valve 11 is open ≥95% and has been running continuously for more than 30 seconds, the auxiliary electric expansion valve 12 is controlled to open to a fixed 100% opening. When the auxiliary electric expansion valve 12 is in the open state, if the opening degree of the main electronic expansion valve 11 is ≤40%, the opening degree of the auxiliary electric expansion valve 12 decreases by 1 level; if the opening degree of the main electronic expansion valve 11 is ≤35%, the opening degree of the auxiliary electric expansion valve 12 decreases by 2 levels; if the opening degree of the main electronic expansion valve 11 is ≤30%, the opening degree of the auxiliary electric expansion valve 12 decreases by 3 levels; if the opening degree of the main electronic expansion valve 11 is ≤25%, the opening degree of the auxiliary electric expansion valve 12 decreases by 4 levels, until the auxiliary electric expansion valve 12 is in the fully closed state.

[0041] In one embodiment, the low-temperature seasonal operation mode includes: The magnetic levitation refrigeration compressor 1 is turned off, the first valve 19 on the gas supply pipe 8 is closed, and the second valve 20 on the first connecting pipe 17 is opened. The gaseous refrigerant output from the gas-liquid separator 3 is transported to the gas inlet of the condenser 2 through the gas supply pipe 8, the first connecting pipe 17, and the exhaust pipe 16. The liquid refrigerant is supplied by gravity between the condenser 2 and the thermosiphon evaporator 4, and the natural cooling capacity extracted by the heat pipe natural cooling circuit is transported to the thermosiphon evaporator 4. The main electronic expansion valve 11 and auxiliary electric expansion valve 12 on the main liquid supply pipe 5 are fully open to reduce the flow resistance of the pipe. The liquid refrigerant is transported from the condenser 2 to the gas-liquid separator 3 by the pressure generated by the vertical installation height difference between the condenser 2 and the gas-liquid separator 3 through the main liquid supply pipe 5.

[0042] In one embodiment, during low-temperature seasonal operation, the cooling capacity adjustment of the heat pipe natural cooling circuit includes: When the refrigerant evaporation temperature is within the preset temperature range, the cooling capacity is adjusted only by regulating the operating frequency of the fan and / or spray water pump of condenser 2. When both the fan and the spray pump have been reduced to the minimum allowable operating frequency, and the refrigerant evaporation temperature is still below the lower limit of the preset temperature range, turn off the fan and the spray pump of condenser 2 to reduce the cooling capacity. When the fan and spray water pump are both turned off, and the refrigerant evaporation temperature is still lower than the lower limit of the preset temperature range, the switch valve 15 on some branches 18 is turned off step by step to reduce the condensing heat exchange area and further reduce the cooling capacity until the refrigerant evaporation temperature rises back to the preset temperature range, and the fan and water pump of the condenser 2 resume the frequency conversion regulation mode. When the fan and spray pump have both increased to the maximum allowable operating frequency and the refrigerant evaporation temperature is still higher than the preset upper limit of temperature, the switch valve 15 on the closed branch 18 is opened step by step to increase the condensing heat exchange area and increase the cooling capacity until the refrigerant evaporation temperature drops back to the preset temperature range.

[0043] In the natural cooling mode of heat pipes during cold seasons, the lower the outdoor ambient temperature, the stronger the heat exchange capacity of the heat pipes, and the lower the evaporation temperature tends to be. Conversely, when the outdoor ambient temperature is relatively high or the user-side heat load is large, the heat exchange capacity of the heat pipes may be insufficient, and the evaporation temperature tends to be high. Therefore, bidirectional adjustment based on evaporation temperature feedback is necessary to match the actual cooling demand.

[0044] When the switching valves 15 on branch 18 are closed or opened in stages, a preset stabilization time is waited after each action. The next closing or opening action is only performed after the rate of change of the refrigerant evaporation temperature is less than a preset threshold. This avoids drastic fluctuations in cooling capacity caused by all switching valves 15 on condenser branch 2 being fully open or closed at the same time, ensuring stable system operation.

[0045] In summary, this invention, through the synergistic optimization of liquid supply method, condensation regulation, and motor cooling, balances energy-saving benefits, temperature control accuracy, and operational safety, and has good potential for widespread application.

[0046] The foregoing description illustrates and describes preferred embodiments of the present application. However, as it is understood, the present 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 present invention through the foregoing teachings or the technology or knowledge in related fields.

Claims

1. A magnetic levitation chiller unit, characterized in that, The system includes a magnetic levitation refrigeration compressor, a condenser, a gas-liquid separator, and a thermosiphon evaporator. The refrigerant outlet of the condenser is connected to the liquid inlet of the gas-liquid separator via a main liquid supply pipe. The liquid outlet of the gas-liquid separator is connected to the liquid inlet of the thermosiphon evaporator via an evaporator liquid inlet pipe. The gas outlet of the thermosiphon evaporator is connected to the gas return port of the gas-liquid separator via an evaporator gas return pipe. The gas outlet of the gas-liquid separator is connected to the suction port of the magnetic levitation refrigeration compressor via a gas supply pipe. The gas outlet of the magnetic levitation refrigeration compressor is connected to the refrigerant inlet of the condenser via an exhaust pipe. The exhaust pipe and the gas supply pipe are connected by a first connecting pipe. A main electronic expansion valve is installed on the main liquid supply pipe, and auxiliary electric expansion valves are connected in parallel at both ends of the main electronic expansion valve. No liquid refrigerant pump is installed on the main liquid supply pipe. The vertical installation height of the condenser is higher than that of the gas-liquid separator. The liquid refrigerant flows from the condenser to the gas-liquid separator through the main liquid supply pipe, relying on the pressure generated by the unit pressure difference and / or the vertical installation height difference between the condenser and the gas-liquid separator.

2. The magnetic levitation chiller unit according to claim 1, characterized in that, The main liquid supply pipe is also equipped with a cooling liquid supply branch pipe, which is connected to the motor cooling inlet of the magnetic levitation refrigeration compressor. The motor cooling outlet of the magnetic levitation refrigeration compressor is connected to the gas-liquid separator through a cooling return pipe. The cooling liquid supply branch pipe is equipped with a check valve and an auxiliary refrigerant pump. The auxiliary refrigerant pump is connected in parallel with the check valve, and the flow direction of the check valve is from the main liquid supply pipe to the motor cooling inlet.

3. A magnetic levitation chiller unit according to claim 1, characterized in that, The condenser includes condenser coils, a fan and / or a spray water pump. The air inlet side of the condenser is provided with several parallel branches, each branch is provided with several sets of condenser coils, and each branch is also provided with a switch valve.

4. A control method for a magnetic levitation chiller unit, characterized in that, The application of the magnetic levitation chiller unit according to any one of claims 1-3 includes: The corresponding operating mode is executed based on the temperature difference between the outdoor ambient temperature and the user's water supply temperature. When the temperature difference is greater than or equal to the first temperature threshold, the high-temperature season operation mode is executed. When the temperature difference is less than the first temperature threshold and the temperature difference is greater than or equal to the second temperature threshold, the transitional season operation mode is executed. When the temperature difference is less than the second temperature threshold, the low-temperature seasonal operation mode is executed. Wherein, the first temperature threshold is greater than the second temperature threshold. During the high-temperature season and transitional season, it operates in compression refrigeration cycle mode, while during the low-temperature season, it switches to heat pipe natural cooling cycle mode.

5. The control method for a magnetic levitation chiller unit according to claim 4, characterized in that, Operating modes during high-temperature seasons include: Turn on the magnetic levitation refrigeration compressor, open the first valve on the gas supply pipe, close the second valve on the first connecting pipe, and the gaseous refrigerant output from the gas-liquid separator enters the magnetic levitation refrigeration compressor through the gas supply pipe for compression, and then is delivered to the air inlet of the condenser through the exhaust pipe for compression refrigeration cycle. Specifically, the main electronic expansion valve on the main liquid supply pipe is opened, and the auxiliary electric expansion valve is closed; the liquid refrigerant is transported from the condenser to the gas-liquid separator through the main liquid supply pipe under the pressure difference drive; In a further preferred embodiment, during the high-temperature season operation mode, the auxiliary refrigerant pump is turned off, and the liquid refrigerant is delivered to the motor cooling inlet by the cooling liquid supply branch pipe under the pressure difference drive; the switching valves on all branches in the condenser are opened.

6. The control method for a magnetic levitation chiller unit according to claim 4, characterized in that, Transitional season operating modes include: Turn on the magnetic levitation refrigeration compressor, open the first valve on the gas supply pipe, close the second valve on the first connecting pipe, and the gaseous refrigerant output from the gas-liquid separator enters the magnetic levitation refrigeration compressor through the gas supply pipe for compression, and then is delivered to the air inlet of the condenser through the exhaust pipe for compression refrigeration cycle. Among them, the main electronic expansion valve on the main liquid supply pipe is opened; the liquid refrigerant is driven by the pressure difference and uses the pressure generated by the vertical installation height difference between the condenser and the gas-liquid separator to be transported from the condenser to the gas-liquid separator through the main liquid supply pipe. The opening signal of the main electronic expansion valve is collected in real time. When the opening of the main electronic expansion valve reaches the set opening threshold, the auxiliary electric expansion valve is opened. Based on the opening signal of the main electronic expansion valve, the opening of the auxiliary electric expansion valve is controlled in stages. In a further preferred embodiment, during the transitional season operation mode, when the unit's operating pressure ratio drops to the minimum pressure ratio threshold required for cooling the magnetic levitation refrigeration compressor, the auxiliary refrigerant pump on the cooling liquid supply branch pipe is turned on to deliver liquid refrigerant to the motor cooling inlet of the magnetic levitation refrigeration compressor.

7. The control method for a magnetic levitation chiller unit according to claim 6, characterized in that, The step-by-step opening control of the auxiliary electric expansion valve based on the opening signal of the main electronic expansion valve includes: When the opening degree of the main electronic expansion valve reaches the fourth opening degree threshold, the auxiliary electric expansion valve is controlled to open to the first opening degree position. When the opening degree of the main electronic expansion valve reaches the third opening degree threshold, the auxiliary electric expansion valve is controlled to open to the second opening degree position. When the opening degree of the main electronic expansion valve reaches the second opening degree threshold, the auxiliary electric expansion valve is controlled to open to the third opening degree position. When the opening degree of the main electronic expansion valve reaches the first opening degree threshold, the auxiliary electric expansion valve is controlled to open to the fourth opening degree position. Among them, the fourth opening threshold < the third opening threshold < the second opening threshold < the first opening threshold, and the fourth opening level > the third opening level > the second opening level > the first opening level.

8. The control method for a magnetic levitation chiller unit according to claim 7, characterized in that, Graded opening control also includes downshift control: When the auxiliary electric expansion valve is in the open state, when the opening degree of the main electronic expansion valve drops to the fifth opening degree threshold, the opening degree of the auxiliary electric expansion valve decreases by one level. When the opening degree of the main electronic expansion valve drops to the sixth opening degree threshold, the opening degree of the auxiliary electric expansion valve decreases by 2 levels. When the opening degree of the main electronic expansion valve drops to the seventh opening degree threshold, the opening degree of the auxiliary electric expansion valve decreases by 3 levels. When the opening degree of the main electronic expansion valve drops to the eighth opening degree threshold, the opening degree of the auxiliary electric expansion valve decreases by 4 levels, that is, the auxiliary electric expansion valve is closed. Among them, the fourth opening threshold > the fifth opening threshold > the sixth opening threshold > the seventh opening threshold > the eighth opening threshold.

9. The control method for a magnetic levitation chiller unit according to claim 4, characterized in that, Low-temperature seasonal operating modes include: Turn off the magnetic levitation refrigeration compressor, close the first valve on the gas supply pipe, open the second valve on the first connecting pipe, and the gaseous refrigerant output from the gas-liquid separator is transported to the gas inlet of the condenser through the gas supply pipe, the first connecting pipe, and the exhaust pipe. The liquid refrigerant is supplied by gravity between the condenser and the thermosiphon evaporator, and the natural cooling capacity extracted by the heat pipe natural cooling circuit is transported to the thermosiphon evaporator. The main electronic expansion valve and auxiliary electric expansion valve on the main liquid supply pipe are fully open. The liquid refrigerant is transported from the condenser to the gas-liquid separator by the pressure generated by the vertical installation height difference between the condenser and the gas-liquid separator through the main liquid supply pipe.

10. The control method for a magnetic levitation chiller unit according to claim 4, characterized in that, During low-temperature season operation, the cooling capacity adjustment of the heat pipe natural cooling circuit includes: When the refrigerant evaporation temperature is within the preset temperature range, the cooling capacity is adjusted only by regulating the operating frequency of the condenser fan and / or the spray water pump. When both the fan and the spray pump have been reduced to the minimum allowable operating frequency, and the refrigerant evaporation temperature is still below the lower limit of the preset temperature range, turn off the fan and the spray pump of the condenser. When the fan and spray pump are both turned off, and the refrigerant evaporation temperature is still below the lower limit of the preset temperature range, the switching valves on some branches are closed one by one until the refrigerant evaporation temperature rises back to the preset temperature range, and the fan and pump of the condenser resume the frequency conversion regulation mode. When both the fan and the spray pump have increased to the maximum allowable operating frequency, and the refrigerant evaporation temperature is still higher than the preset upper limit of temperature, the switch valves on the closed branches are opened one by one until the refrigerant evaporation temperature drops back to the preset temperature range.

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