Multi-operation mode refrigeration system based on chilled water pre-cooling and control method

Abstract

This application discloses a multi-mode refrigeration system and control method based on chilled water precooling, comprising: a chiller unit, a natural cooling device, a first branch pipe, a second branch pipe, a third branch pipe, a first control valve, a second control valve, a third control valve, a fourth control valve, a first circulating pump, and a second circulating pump; the chiller unit includes a condenser and an evaporator, the evaporator being connected to a chilled water outlet pipe and a chilled water return pipe; the natural cooling device is connected to the condenser via a cooling water outlet pipe and a cooling water return pipe; the first end of the first branch pipe, the first control valve, the first end of the second branch pipe, and the first circulating pump are sequentially connected to the chilled water return pipe along the flow direction of the chilled water; the second circulating pump, the second end of the second branch pipe, the third control valve, and the second end of the first branch pipe are sequentially connected to the cooling water outlet pipe along the flow direction of the cooling water; both ends of the third branch pipe are connected to the cooling water outlet pipe and are equipped with a fifth control valve. This application can flexibly achieve seamless pressure stabilization switching between three modes: conventional cooling, pre-cooling cooling, and natural cooling. It extends the natural cooling time throughout the year, improves the overall cooling performance coefficient of the system throughout the year, reduces the system's annual energy consumption, and eliminates the need for additional plate heat exchangers. The piping structure is simpler, reducing heat exchange losses and flow resistance of cooling water and chilled water. In addition, it can ensure that the flow resistance of chilled water remains stable in multiple modes, ultimately ensuring stable terminal pressure.

Description

Technical Field

[0001] This application relates to the field of refrigeration equipment technology, and more specifically, to a multi-mode refrigeration system and control method based on chilled water precooling. Background Technology

[0002] In the field of refrigeration system applications, whether in industrial production, data centers, or commercial buildings, the energy efficiency, operational stability, and reliability of terminal cooling are key concerns. Among these, stable chilled water pressure is a crucial prerequisite for ensuring the normal operation and efficient adjustment of terminal equipment, and preventing equipment damage. As a closed-loop system, stable chilled water pressure prevents localized negative pressure that could lead to water vaporization, avoids pump cavitation, and ensures stable heating and cooling effects for terminal equipment, extending equipment lifespan. Instable pressure, on the other hand, can cause fluctuations in heating and cooling effects, or even lead to pump cavitation, abnormal pipe noises, and equipment damage.

[0003] Traditional refrigeration systems have significant limitations. They rely on a single compressor for refrigeration and depend on the continuous operation of the chiller compressor throughout the year. During transitional seasons and nighttime periods of low outdoor temperatures, they cannot effectively utilize natural outdoor cooling sources, resulting in significant energy waste and high operating costs. Furthermore, the single-mode operation makes it difficult to adapt to load fluctuations in different seasons, further impacting system operating efficiency.

[0004] To address the high energy consumption of traditional refrigeration systems, the industry has gradually developed multi-mode refrigeration systems capable of natural cooling, mechanical cooling, or pre-cooling. However, existing systems still have many shortcomings that need to be addressed. On the one hand, existing conventional natural cooling energy-saving systems often utilize natural cold sources by adding plate heat exchangers, resulting in complex piping structures, significant heat exchange losses, and an increase in potential failure points. This not only increases maintenance costs but also reduces the annual utilization rate of the natural cold source. On the other hand, the operating condition classification of existing dual-mode natural cooling systems is rather crude, simply distinguishing between full machine cooling and full natural cooling modes. This fails to adapt to the frequent temperature fluctuations during the spring and autumn transition seasons and makes it difficult to classify and match dynamic loads at the terminal, leading to frequent compressor start-ups and shutdowns. This not only increases equipment wear but also causes poor stability in the water supply temperature.

[0005] More importantly, even existing refrigeration systems capable of switching between natural cooling, mechanical cooling, and pre-cooling modes suffer from fundamental problems such as unreasonable piping design, inadequate valve configuration, and imperfect control logic. Specifically, the path of chilled water through different equipment varies when switching between operating modes, with some equipment ceasing to participate in chilled water circulation under certain modes. Simultaneously, the operating status of the circulation pump changes with mode switching. The pressure stability of the chilled water is closely related to the consistency of the circulation path and the continuous operation of the circulation pump. As a core component of the refrigeration system, the continuous operation of the circulation pump ensures that chilled water circulates within the system at a stable flow rate and pressure, guaranteeing heat exchange efficiency and system reliability. Once the circulation path changes or the circulation pump starts and stops, it causes a sudden change in the flow resistance of the chilled water, leading to chilled water pressure fluctuations and ultimately unstable terminal pressure. This instability in terminal pressure directly affects the cooling effect at the terminal, leading to abnormal equipment operation. In severe cases, pressure fluctuations can cause pipe leaks, water pump cavitation, and other malfunctions, shortening the overall service life of the system. It cannot meet the stringent requirements for terminal pressure stability in high-precision cooling scenarios (such as data centers)—such scenarios have extremely low tolerance for fluctuations in the supply and return pressure difference of chilled water, and existing systems are unable to meet this standard. Summary of the Invention

[0006] The main objective of this application is to provide a multi-mode refrigeration system and control method based on chilled water precooling, in order to solve the technical problems of insufficient energy efficiency, poor adaptability to operating conditions, and especially the instability of chilled water and terminal pressure under different operating modes in related technologies.

[0007] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description or may be learned by practice of this application.

[0008] According to a first aspect of this application, a multi-mode refrigeration system based on chilled water precooling is provided, comprising: a chiller unit, a natural cooling device, a first branch pipe, a second branch pipe, a first control valve, a second control valve, a third control valve, a fourth control valve, a first circulation pump, and a second circulation pump; wherein, The chiller unit includes a condenser and an evaporator, the evaporator being connected to a chilled water outlet pipe and a chilled water return pipe; the natural cooling equipment is connected to the condenser via a cooling water outlet pipe and a cooling water return pipe. The first end of the first branch pipe, the first control valve, the first end of the second branch pipe, and the first circulating pump are sequentially connected to the chilled water return pipe along the flow direction of the chilled water; The second circulating pump, the second end of the second branch pipe, the third control valve, and the second end of the first branch pipe are sequentially connected to the cooling water outlet pipe along the flow direction of the cooling water.

[0009] In one exemplary embodiment of this application, a third branch pipe is further included, wherein a fifth control valve is provided on the third branch pipe; The two ends of the third branch pipe are respectively connected to the first position and the second position of the cooling water outlet pipe. The first position is located between the second circulating pump and the second end of the second branch pipe, and the second position is located between the second end of the first branch pipe and the condenser.

[0010] In one exemplary embodiment of this application, a first constant pressure water supply device is also included, which is connected to the chilled water return pipe at a position between the first circulation pump and the first end of the second branch pipe; The second constant pressure water supply device is connected to the cooling water outlet pipe at a position between the second circulating pump and the natural cooling equipment.

[0011] In one exemplary embodiment of this application, a dosing device is also included, connected to the cooling water outlet pipe at a position between the second circulating pump and the natural cooling device.

[0012] In one exemplary embodiment of this application, a first bypass pipe is further included, which connects the cooling water outlet pipe and the cooling water return pipe and is close to the condenser. The first bypass pipe is provided with a control valve. The second bypass pipe connects the chilled water return pipe and the chilled water outlet pipe, and is located near the evaporator. The second bypass pipe is equipped with a control valve.

[0013] In one exemplary embodiment of this application, the natural cooling device is at least one of a cooling tower or a dry cooler.

[0014] In one exemplary embodiment of this application, the multi-operating-mode refrigeration system further includes: At least two chilled water temperature sensors are respectively installed in the chilled water outlet pipe and the chilled water return pipe; At least three chilled water side pressure sensors are respectively installed at the chilled water outlet pipe, the chilled water return pipe and the outlet of the first circulation pump; A chilled water flow meter is installed on the chilled water outlet pipe; At least three test terminals are reserved on the chilled water side, respectively located at the chilled water outlet pipe, the chilled water return pipe, and the outlet of the first circulation pump.

[0015] In one exemplary embodiment of this application, the multi-operating-mode refrigeration system further includes: At least two cooling water side temperature sensors are respectively installed in the cooling water outlet pipe and the cooling water return pipe; At least three cooling water side pressure sensors are respectively installed at the cooling water outlet pipe, the cooling water return pipe and the outlet of the second circulation pump; A cooling water flow meter is installed on the cooling water outlet pipe; At least three test terminals are reserved on the cooling water side, respectively located at the cooling water outlet pipe, the cooling water return pipe, and the outlet of the second circulation pump.

[0016] According to a second aspect of this application, a control method for a multi-operation mode refrigeration system based on chilled water precooling is provided, for controlling the above-mentioned multi-operation mode refrigeration system to perform at least one of the following refrigeration modes; Normal cooling mode: Open the first and third control valves, and close the second and fourth control valves; The first circulation pump controls the chilled water to enter the evaporator through the chilled water return pipe for active cooling, and then flows to the end through the chilled water outlet pipe. The cooling water is controlled by the second circulation pump to enter the condenser through the cooling water outlet pipe for heat exchange, and then returns to the natural cooling equipment through the cooling water return pipe. Pre-cooling mode; Close the first and third control valves, and open the second and fourth control valves; Chilled water from the end enters the condenser through the first branch pipe and the cooling water outlet pipe, and then enters the natural cooling equipment for pre-cooling through the cooling water return pipe; The pre-cooled chilled water is controlled by the second circulation pump to flow into the second branch pipe through the cooling water outlet pipe; The pre-cooled chilled water is controlled by the first circulation pump to enter the evaporator for active cooling through the chilled water return pipe, and after cooling, it flows to the end through the chilled water outlet pipe. Natural cooling mode; Close the first and third control valves, open the second and fourth control valves, and shut down the evaporator; Chilled water from the end enters the condenser through the first branch pipe and the cooling water outlet pipe, and then enters the natural cooling equipment for refrigeration through the cooling water return pipe; The chilled water after cooling is controlled by the second circulation pump to flow into the second branch pipe through the cooling water outlet pipe; The chilled water, after being cooled, flows through the evaporator via the chilled water return pipe and then through the chilled water outlet pipe to the end via the first circulation pump.

[0017] In one exemplary embodiment of this application, the multi-operation mode refrigeration system further includes a third branch pipe, on which a fifth control valve is provided; The two ends of the third branch pipe are respectively connected to the first position and the second position of the cooling water outlet pipe. The first position is located between the second circulating pump and the second end of the second branch pipe, and the second position is located between the second end of the first branch pipe and the condenser. The process of executing the pre-cooling mode or the natural cooling mode also includes: The flow rate of chilled water to the evaporator is controlled by adjusting the opening of the fifth control valve.

[0018] The exemplary embodiments of this application may have some or all of the following beneficial effects: To address the shortcomings of existing refrigeration systems, such as insufficient energy efficiency, poor adaptability to operating conditions, complex piping, and unstable chilled water and terminal pressures under different modes, the multi-mode refrigeration system based on chilled water precooling described in claim 1 of this application achieves significant technical effects through a reasonable piping architecture design, precise valve configuration, and clear mode switching logic, combined with the coordinated operation of three refrigeration modes, as detailed below: On the one hand, by switching the first to fourth control valves in an orderly manner, seamless switching between three modes—conventional cooling, pre-cooling cooling, and natural cooling—can be flexibly achieved to adapt to cooling needs of different seasons and loads. In conventional cooling mode, the first and third control valves are opened, while the second and fourth control valves are closed. The first circulation pump controls the chilled water to enter the evaporator for active cooling through the chilled water return pipe, while the second circulation pump controls the cooling water to circulate and exchange heat between the condenser and the natural cooling equipment. This can meet the high-load cooling needs during high-temperature seasons and ensure cooling efficiency. In pre-cooling cooling mode, the first and third control valves are closed, while the second and fourth control valves are opened. The terminal chilled water first enters the condenser through the first branch pipe and the cooling water outlet pipe, and then enters the natural cooling equipment for pre-cooling through the cooling water return pipe. After pre-cooling, the water is sent to the evaporator for further active cooling via the second circulation pump, the second branch pipe, and the first circulation pump. This fully utilizes the outdoor low-temperature natural cold source during the transition season, reduces the evaporator's cooling load, lowers compressor energy consumption, and solves the problem of traditional systems being unable to utilize natural cold sources and resulting in significant energy waste during the transition season. In natural cooling mode, the first and third control valves are closed, the second and fourth control valves are opened, and the evaporator is closed. The terminal chilled water is cooled via the first branch pipe, condenser, and natural cooling equipment, and then returns to the terminal via the second circulation pump, the second branch pipe, the first circulation pump, and the evaporator. This allows for complete cooling by utilizing natural cold sources during periods of low outdoor temperature, such as at night and in winter, completely stopping the compressor and maximizing energy savings. This solves the problems of low utilization and high energy consumption in existing natural cooling systems.

[0019] Secondly, the refrigeration system in this embodiment does not require an additional plate heat exchanger. Through a rational layout of the chiller unit, natural cooling equipment, two branch pipes, and four control valves, combined with the coordinated operation of the first and second circulating pumps, it can switch between three modes. Compared to existing systems that require additional plate heat exchangers, the piping structure is simpler, reducing heat exchange losses and flow resistance of cooling and chilled water. There is no intermediate secondary heat exchange loss, allowing it to switch to natural cooling mode at higher outdoor temperatures. Chilled water temperature control is more precise, and the terminal temperature control is excellent. Furthermore, it reduces the number of potential failure points, lowering equipment procurement costs and reducing daily maintenance workload and costs, while improving system reliability and avoiding frequent failures caused by complex piping. In addition, this embodiment integrates chilled water and cooling water into a closed-loop circulation system, resulting in shorter piping paths, lower circulation resistance, and no additional local resistance losses from plate heat exchangers. The circulating water pumps also consume less power throughout the year, further reducing overall annual energy consumption.

[0020] Thirdly, in this embodiment, when switching between the three cooling modes, precise valve control ensures that chilled water always flows through the same core equipment. Specifically, in the normal cooling mode, pre-cooling cooling mode, and natural cooling mode, chilled water always passes through the evaporator, and the first and second circulation pumps remain running in all modes, without changing their start / stop status during mode switching. Specifically, in the normal cooling mode, chilled water circulates through the first circulation pump and the evaporator, while cooling water circulates through the second circulation pump, the condenser, and the natural cooling equipment. In the pre-cooling cooling mode, chilled water circulates sequentially through the first branch pipe, the condenser, the natural cooling equipment, the second circulation pump, the second branch pipe, the first circulation pump, and the evaporator. In the natural cooling mode, chilled water circulates sequentially through the first branch pipe, the condenser, the natural cooling equipment, the second circulation pump, the second branch pipe, the first circulation pump, and the evaporator (the evaporator only provides circulation and does not cool). In all three modes, although the chilled water circulation path branches and switches, the core equipment (condenser, evaporator, and natural cooling equipment) remains consistent, and the dual circulation pumps operate continuously. This ensures that the flow resistance of the chilled water remains stable, avoiding pressure fluctuations caused by sudden changes in the circulation path or pump start-stop operations. This results in stable chilled water pressure, ultimately guaranteeing stable terminal pressure and meeting the stringent requirements of high-precision cooling scenarios such as data centers for minimal fluctuations in the supply and return pressure difference of chilled water. Simultaneously, stable terminal pressure effectively prevents pump cavitation, pipe noise, leaks, and other malfunctions, ensuring stable heating and cooling performance of terminal equipment, extending the lifespan of the system and terminal equipment, and resolving the problems of high equipment wear and unreliable operation caused by unstable pressure in existing systems.

[0021] Fourthly, in this embodiment, by setting a pre-cooling mode, the synergy between natural cold source and mechanical refrigeration is achieved during the transition season. This allows for graded matching of dynamic loads at the terminal, avoiding the frequent start-stop problems of compressors caused by the coarse division of operating conditions in existing systems. This reduces mechanical wear on the compressor and extends its service life. At the same time, the continuous operation of the dual circulation pump and the stable chilled water pressure ensure stable chilled water flow, thereby guaranteeing stable water supply temperature. This prevents water temperature fluctuations from affecting the cooling effect at the terminal, further improving the reliability and comfort of the system operation.

[0022] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0023] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application. In the drawings: Figure 1 This is a structural schematic diagram based on an embodiment of this application; The components include: 1. Chiller unit; 100. Condenser; 110. Evaporator; 2. First circulating pump; 3. Second circulating pump; 4. Natural cooling equipment; 5. Dosing device; 60. First constant pressure water supply device; 61. Second constant pressure water supply device; 7. Chilled water return pipe; 8. Chilled water outlet pipe; 9. Cooling water return pipe; 10. Cooling water outlet pipe; 11. First branch pipe; 12. Second branch pipe; 13. First bypass pipe; 14. Second bypass pipe; 15. Third branch pipe. Detailed Implementation

[0024] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore their detailed descriptions will be omitted. Furthermore, the drawings are merely illustrative of this application and are not necessarily drawn to scale.

[0025] Although relative terms such as "upper" and "lower" are used in this specification to describe the relative relationship of one component of an icon to another, these terms are used only for convenience, such as according to the orientation of the examples in the accompanying drawings. It is understood that if the device of the icon is flipped so that it is upside down, the component described as "upper" will become the component described as "lower." When a structure is "upper" of another structure, it may mean that the structure is integrally formed on the other structure, or that the structure is "directly" mounted on the other structure, or that the structure is "indirectly" mounted on the other structure through another structure.

[0026] The terms “a,” “one,” “the,” and “at least one” are used to indicate the existence of one or more elements / components / etc.; the terms “including” and “having” are used to indicate an open-ended inclusion and to mean that there may be other elements / components / etc. in addition to the listed elements / components / etc.; the terms “first” and “second” are used only as markers and are not a limitation on the number of objects.

[0027] Furthermore, the terms "set up," "equipped with," "connected," and "fixed" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0028] In addition, the term "multiple" should mean two or more.

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments. Example 1

[0030] like Figure 1 As shown, this embodiment provides a multi-mode refrigeration system based on chilled water precooling, including: a chiller unit 1, a natural cooling device 4, a first branch pipe 11, a second branch pipe 12, a first control valve V1, a second control valve V2, a third control valve V3, a fourth control valve V4, a first circulation pump 2, and a second circulation pump 3. The connection relationships and functions of each component are as follows: The chiller unit 1 is the core refrigeration component of the refrigeration system. It integrates a condenser 100 and an evaporator 110. The two work independently and collaboratively to realize the functions of heat exchange of cooling water and cooling of chilled water, respectively. The evaporator 110 has its inlet end connected to the chilled water return pipe 7 and its outlet end connected to the chilled water outlet pipe 8. After the chilled water is cooled by the evaporator 110, it is transported to the terminal cooling equipment through the chilled water outlet pipe 8. After the terminal heat exchange, it flows back to the evaporator 110 through the chilled water return pipe 7, forming a closed loop of chilled water. The natural cooling equipment 4 is used to achieve heat exchange or cooling by utilizing outdoor natural cold sources. Its inlet end is connected to the cooling water outlet pipe 10 and its outlet end is connected to the cooling water return pipe 9. The other end of the cooling water return pipe 9 is connected to the outlet end of the condenser 100, and the other end of the cooling water outlet pipe 10 is connected to the inlet end of the condenser 100. This forms a closed loop of cooling water between the natural cooling equipment 4 and the condenser 100, achieving cooling water cooling after heat exchange in the condenser 100.

[0031] The first end of the first branch pipe 11, the first control valve V1, the first end of the second branch pipe 12, and the first circulation pump 2 are sequentially connected to the chilled water return pipe 7 along the flow direction of the chilled water, wherein the first circulation pump 2 is used to provide power for the chilled water circulation; the second circulation pump 3, the second end of the second branch pipe 12, the third control valve V3, and the second end of the first branch pipe 11 are sequentially connected in series to the cooling water outlet pipe 10 along the flow direction of the cooling water, wherein the second circulation pump 3 is used to provide power for the cooling water circulation and the chilled water precooling / natural refrigeration circulation.

[0032] In this embodiment, when switching between the three cooling modes, precise valve control ensures that the chilled water always flows through the same core equipment. That is, in the normal cooling mode, the pre-cooling cooling mode and the natural cooling mode, the chilled water always passes through the evaporator 110, and the first circulation pump 2 and the second circulation pump 3 remain running in all modes and do not change their start or stop status when switching modes.

[0033] Specifically, in the conventional cooling mode, chilled water circulates through the first circulation pump 2 and evaporator 110, while cooling water circulates through the second circulation pump 3, condenser 100, and natural cooling device 4. In the pre-cooling cooling mode, chilled water circulates sequentially through the first branch pipe 11, condenser 100, natural cooling device 4, second circulation pump 3, second branch pipe 12, first circulation pump 2, and evaporator 110. In the natural cooling mode, chilled water circulates sequentially through the first branch pipe 11, condenser 100, natural cooling device 4, second circulation pump 3, second branch pipe 12, first circulation pump 2, and evaporator 110 (evaporator 110 only provides circulation and does not provide cooling). In all three modes, although the chilled water circulation path branches and switches, the core equipment (condenser 100, evaporator 110, and natural cooling equipment 4) remains consistent, and the dual circulation pumps operate continuously. This ensures that the flow resistance of the chilled water remains stable, avoiding pressure fluctuations caused by sudden changes in the circulation path or the start and stop of the circulation pumps. This results in stable chilled water pressure, ultimately guaranteeing stable terminal pressure and meeting the stringent requirements of high-precision cooling scenarios such as data centers for minimal fluctuations in the supply and return pressure difference of chilled water. Simultaneously, stable terminal pressure effectively prevents pump cavitation, abnormal pipe noise, leaks, and other malfunctions, ensuring stable heating and cooling effects of the terminal equipment, extending the service life of the system and terminal equipment, and resolving the problems of high equipment wear and unreliable operation caused by unstable pressure in existing systems.

[0034] As can be seen from the above cycle process, the refrigeration system in this embodiment does not require the addition of a plate heat exchanger. Only through the reasonable layout of the chiller unit 1, natural cooling device 4, two branch pipes, and four control valves, combined with the coordinated operation of the first and second circulating pumps 3, the switching between three modes can be achieved. Compared to existing systems that add plate heat exchangers, the piping structure is simpler, reducing heat exchange losses and flow resistance of cooling water and chilled water. There is no intermediate secondary heat exchange loss, allowing the system to switch to natural cooling mode at lower outdoor temperatures. Chilled water temperature control is more precise, and the terminal temperature control is excellent. Furthermore, the number of potential failure points is reduced, lowering equipment procurement costs and daily maintenance workload and costs, while improving system reliability and avoiding frequent failures caused by complex piping. In addition, in this embodiment, the chilled water and cooling water are integrated into a closed-loop circulation system, resulting in shorter piping paths, lower circulation resistance, and no additional local resistance losses from plate heat exchangers. The circulating water pumps also consume less power throughout the year, further reducing overall annual energy consumption.

[0035] In this embodiment, the natural cooling device 4 can be at least one of a cooling tower or a dry cooler, which can be flexibly selected according to the actual application scenario (such as outdoor temperature, humidity, and cooling load): when the outdoor temperature is high and the humidity is low, a closed-circuit cooling tower can be used to achieve efficient cooling by utilizing evaporative heat dissipation. Specifically, the closed-circuit cooling tower can be a crossflow closed-circuit tower, a counterflow closed-circuit tower, or a combined closed-circuit cooling tower. When the outdoor temperature is low and evaporative heat dissipation is not required, a dry cooler can be used to achieve cooling through the sensible heat exchange between air and cooling water. The two can also be used in combination to improve the utilization rate of natural cold sources in all seasons.

[0036] Chiller unit 1 can be a screw chiller, scroll chiller, centrifugal chiller, etc., and can be flexibly selected according to the actual cooling load requirements to adapt to different application scenarios, thereby improving the applicability and practicality of the system. At the same time, the various types of chiller units 1 are highly compatible with the piping and valve configuration of this system, which can ensure the smooth switching of multiple modes and further guarantee the reliability of system operation. Example 2

[0037] Based on Example 1, this exemplary embodiment further optimizes the system regulation performance by adding a third branch pipe 15 and a fifth control valve V5. The specific structure is as follows: the two ends of the third branch pipe 15 are respectively connected to the first position and the second position of the cooling water outlet pipe 10, wherein the first position is located between the second circulation pump 3 and the second end of the second branch pipe 12, and the second position is located between the second end of the first branch pipe 11 and the condenser 100; the fifth control valve V5 is fixedly installed on the third branch pipe 15 and is used to control the on / off state of the third branch pipe 15 and the medium flow rate.

[0038] After adding the third branch pipe 15 and the fifth control valve V5, the flow rate of the medium flowing to the condenser 100 and subsequent equipment can be flexibly adjusted. Especially in the pre-cooling refrigeration mode and the natural refrigeration mode, the flow rate of chilled water to the evaporator 110 (or the evaporator 110 as a passage) can be precisely controlled by adjusting the opening of the fifth control valve V5, thereby adapting to the dynamic load changes at the terminal, further improving the system's operational stability and refrigeration efficiency, and avoiding problems such as pressure fluctuations or poor refrigeration effect caused by flow fluctuations.

[0039] The first control valve V1, the second control valve V2, the third control valve V3, and the fourth control valve V4 can be either an electric on / off valve or an electric butterfly valve. The fifth control valve V5 can be either a pressure-independent regulating valve or an electronic dynamic balance regulating valve. All of them can achieve the same on / off switching and flow regulation functions without changing the overall system operation logic and energy-saving effect.

[0040] The first circulation pump 2 and the second circulation pump 3 can be operated as constant-speed pumps or as variable frequency pumps to adaptively adjust their speed. The variable frequency pump can adaptively adjust its speed according to changes in the terminal load, further reducing energy consumption. At the same time, it ensures the stability of chilled water flow and pressure, enhances the technical effect of terminal pressure stability, and, together with the logic of continuous operation of the dual circulation pumps, further ensures the stability of chilled water flow resistance, improves the stability of water supply temperature, avoids water temperature fluctuations affecting the terminal cooling effect, and further improves the reliability and comfort of system operation.

[0041] To further ensure pressure stability in the chilled water and cooling water systems and avoid pressure fluctuations caused by media loss and temperature changes, such as Figure 1 As shown, this exemplary embodiment, based on Embodiment 1, adds a first constant pressure water supply device 60 and a second constant pressure water supply device 61: The first constant pressure water supply device 60 is connected to the chilled water return pipe 7, specifically located between the first end of the first circulating pump 2 and the second branch pipe 12. Its function is to replenish the lost medium in the chilled water system and maintain the stable pressure of the chilled water system, preventing problems such as negative pressure and cavitation in the chilled water system, and ensuring the stability of the chilled water circulation. The second constant pressure water supply device 61 is connected to the cooling water outlet pipe 10, specifically located between the second circulating pump 3 and the natural cooling device 4. It is used to replenish the medium in the cooling water system, stabilize the pressure of the cooling water system, avoid pressure fluctuations caused by cooling water loss or temperature changes, and ensure the smooth operation of the cooling water circulation and the chilled water precooling / natural refrigeration circulation.

[0042] To prevent the growth of bacteria and scale in the cooling water system and extend the service life of the equipment, this exemplary embodiment adds a dosing device 5 based on the above embodiments. The dosing device 5 is connected to the cooling water outlet pipe 10 and is located between the second circulation pump 3 and the natural cooling equipment 4. It can add scale inhibitors, bactericides and other agents to the cooling water system to inhibit scale formation and bacterial growth, avoid pipe blockage and equipment corrosion, reduce system operation and maintenance costs, and improve system reliability.

[0043] To facilitate system maintenance and debugging, this exemplary embodiment is based on the above embodiments, such as... Figure 1As shown, a first bypass pipe 13 and a second bypass pipe 14 are added: The first bypass pipe 13 connects the cooling water outlet pipe 10 and the cooling water return pipe 9, and its connection position is close to the condenser 100. When the condenser 100 needs maintenance or malfunctions, the pipe valves at both ends of the condenser 100 can be closed, and the control valve of the first bypass pipe 13 can be opened, allowing the cooling water to circulate directly through the first bypass pipe 13, avoiding system shutdown and ensuring the normal operation of other components such as the natural cooling equipment 4. At the same time, the cooling water circulation process can be tested with the condenser 100 closed; The second bypass pipe 14 connects the chilled water return pipe 7 and the chilled water outlet pipe 8, and its connection position is close to the evaporator 110. When the evaporator 110 needs maintenance or malfunctions, the pipe valves at both ends of the evaporator 110 can be closed, and the control valve of the second bypass pipe 14 can be opened, allowing the chilled water to flow directly back to the terminal through the second bypass pipe 14, temporarily ensuring terminal cooling, and facilitating the maintenance of the evaporator 110, thus improving the system's operation and maintenance convenience. The chilled water circulation process can also be adjusted with the evaporator 110 turned off.

[0044] In one embodiment, to facilitate the detection of chilled water temperature, pressure, and flow rate during system operation, the multi-mode refrigeration system further includes: two chilled water-side temperature sensors (21, 22), respectively located on the chilled water outlet pipe 8 and the chilled water return pipe 7; three chilled water-side pressure sensors (23, 24, 25), one located on the chilled water outlet pipe 8 and the other two located on the chilled water return pipe 7 and respectively located at both ends of the first circulation pump 2; a chilled water-side flow meter 26, located on the chilled water outlet pipe 8; and three chilled water-side reserved test terminals (27, 28, 29), one located on the chilled water outlet pipe 8 and the other two located on the chilled water return pipe 7 and respectively located at both ends of the first circulation pump 2.

[0045] To facilitate the monitoring of cooling water temperature, pressure, and flow rate during system operation, the multi-mode refrigeration system also includes: two cooling water-side temperature sensors (31, 32), respectively located on the cooling water outlet pipe 10 and the cooling water return pipe 9; three cooling water-side pressure sensors (33, 34, 35), one located on the cooling water outlet pipe 10 and the other two located on the cooling water return pipe 9 at both ends of the first circulation pump 2; one cooling water-side flow meter 36, located on the cooling water outlet pipe 10; and three reserved test terminals on the cooling water side (37, 38, 39), one located on the cooling water outlet pipe 10 and the other two located on the cooling water return pipe 9 at both ends of the second circulation pump 3.

[0046] Example 3 This embodiment provides a control method for controlling any of the multi-operation mode refrigeration systems described in the above embodiments. The method allows for flexible switching between at least one of the following modes: conventional refrigeration mode, pre-cooling refrigeration mode, and natural refrigeration mode, based on outdoor temperature, terminal load, and other operating conditions. The specific control logic for each mode is as follows: Normal cooling mode This mode is suitable for scenarios with high outdoor temperatures (such as summer) and high terminal loads. It relies on the evaporator 110 of the chiller unit 1 to achieve active cooling. The specific control steps are as follows: open the first control valve V1 and the third control valve V3, and close the second control valve V2 and the fourth control valve V4; start the first circulation pump 2 and the second circulation pump 3 (both are always running and do not start or stop with mode switching). The first circulation pump 2 provides power to control the chilled water to enter the evaporator 110 through the chilled water return pipe 7. The refrigerant in the evaporator 110 exchanges heat with the chilled water to achieve active cooling of the chilled water. The cooled chilled water flows to the terminal cooling equipment through the chilled water outlet pipe 8 to meet the peak high-load cooling demand. At the same time, the second circulation pump 3 provides power to control the cooling water to enter the condenser 100 through the cooling water outlet pipe 10. The cooling water exchanges heat with the high-temperature refrigerant in the condenser 100. After absorbing heat, the cooling water returns to the natural cooling equipment 4 through the cooling water return pipe 9. After being cooled by the natural cooling equipment 4, it is recycled to ensure that the condenser 100 continues to work stably. This mode, one of the three modes, is adapted to high-temperature and high-load operating conditions. The continuous operation of the dual circulation pump ensures stable chilled water pressure and avoids terminal pressure fluctuations. At the same time, relying on the simple piping architecture, it reduces heat exchange losses and ensures refrigeration efficiency and operational reliability.

[0047] Pre-cooling mode This mode is suitable for transitional seasons (such as spring and autumn), when outdoor temperatures are moderate, and the cold source can pre-cool the water but cannot completely and independently meet the entire cooling demand of the terminal units. It utilizes natural cold sources to pre-cool the chilled water, reducing the cooling load on chiller unit 1 and achieving energy-saving operation. The specific control steps are as follows: close the first control valve V1 and the third control valve V3, and open the second control valve V2 and the fourth control valve V4; start the first circulation pump 2 and the second circulation pump 3. The high-temperature chilled water from the terminal cooling equipment is diverted through the chilled water return pipe 7 and flows through the first branch pipe 11 and the cooling water outlet pipe. The chilled water enters the condenser 100 via the cooling water return pipe 9 and then enters the natural cooling equipment 4, where it is pre-cooled by the outdoor natural cold source. Under the action of the second circulation pump 3, the pre-cooled chilled water flows through the cooling water outlet pipe 10 into the second branch pipe 12, and then through the second branch pipe 12 to the chilled water return pipe 7. Subsequently, under the action of the first circulation pump 2, the pre-cooled chilled water enters the evaporator 110 via the chilled water return pipe 7, where it undergoes further active cooling. The cooled chilled water then flows to the terminal via the chilled water outlet pipe 8, completing the chilled water circulation. During this process, because the chilled water is pre-cooled before entering the evaporator 110, the evaporator 110 only needs to supplement a small amount of cooling capacity to bring the chilled water to the terminal supply temperature.

[0048] This mode fully utilizes the outdoor low-temperature natural cooling source during the transitional season, reducing the cooling load of chiller unit 1, lowering compressor energy consumption, and solving the problem of traditional systems being unable to utilize natural cooling sources and resulting in significant energy waste during the transitional season. Simultaneously, by setting a pre-cooling mode, it achieves synergy between natural cooling sources and mechanical refrigeration, allowing for tiered matching of dynamic loads at the terminals. This avoids the frequent compressor start-stop problems caused by the coarse division of operating conditions in existing systems, reducing compressor mechanical wear and extending compressor lifespan. Furthermore, the chilled water system and cooling water system operate in a mixed series and collaborative manner. The pipeline circulation power is provided by the coupled chilled water pump and cooling water pump. The continuous operation of the dual circulation pumps ensures stable chilled water flow resistance, further guaranteeing stable chilled water and terminal pressure. At the same time, relying on the integrated closed-loop circulation design, the circulation resistance is low, and the pump unit's operating power consumption is low, further improving energy-saving effects.

[0049] If the system is equipped with a third branch pipe 15 and a fifth control valve V5 (as in Example 2), the flow rate of chilled water to the evaporator 110 can be adjusted by controlling the opening of the fifth control valve V5 during the pre-cooling refrigeration mode. This allows for precise matching of the dynamic load at the terminal, further optimizing refrigeration efficiency and pressure stability, better achieving synergy between natural cold source and mechanical refrigeration, reducing compressor start-stop frequency, reducing equipment wear, and solving the defects of poor adaptability and high equipment wear in the existing system. At the same time, it further ensures stable water supply temperature and improves the comfort of terminal cooling.

[0050] Natural cooling mode This mode is suitable for scenarios with low outdoor temperatures (such as winter or nighttime). It can fully utilize natural cold sources for cooling, eliminating the need for chiller unit 1 to operate and maximizing energy savings. The specific control steps are as follows: close the first control valve V1 and the third control valve V3, open the second control valve V2 and the fourth control valve V4, and simultaneously shut down chiller unit 1 (stopping the cooling function of chiller unit 1; evaporator 110 only serves as a chilled water passage); start the first circulation pump 2 and the second circulation pump 3. High-temperature chilled water from the terminal cooling equipment is diverted through the chilled water return pipe 7, enters the condenser 100 through the first branch pipe 11 and the cooling water outlet pipe 10, and then undergoes cooling... The water return pipe 9 enters the natural cooling equipment 4, utilizing the outdoor natural cold source to complete the refrigeration of the chilled water. Under the action of the second circulation pump 3, the refrigerated chilled water flows through the cooling water outlet pipe 10 into the second branch pipe 12, and then through the second branch pipe 12 to the chilled water return pipe 7. Subsequently, under the action of the first circulation pump 2, the refrigerated chilled water flows through the chilled water return pipe 7 through the evaporator 110 (passage only), and then through the chilled water outlet pipe 8 to the end, completing the chilled water circulation. At this time, the compressor stops running, and refrigeration is achieved entirely by relying on the natural cold source, maximizing energy savings and solving the defects of low utilization and high energy consumption in the existing natural cooling system.

[0051] Meanwhile, the first circulation pump 2 and the second circulation pump 3 operate continuously, and the chilled water always flows through the same core equipment (condenser 100, evaporator 110, and natural cooling equipment 4), ensuring that the flow resistance of the chilled water remains stable. This avoids pressure fluctuations caused by sudden changes in the circulation path or the start and stop of the circulation pumps, thereby achieving stable chilled water pressure and ultimately ensuring stable terminal pressure. This meets the stringent requirements of high-precision cooling scenarios such as data centers for small fluctuations in the supply and return pressure difference of chilled water. In addition, relying on the simple piping architecture that does not require the addition of plate heat exchangers, there is no secondary heat loss. This mode can be switched at higher outdoor temperatures, resulting in more precise chilled water temperature control, excellent terminal constant temperature effect, and reduced failure points, thus improving the reliability of system operation.

[0052] Similarly, if the system is equipped with a third branch pipe 15 and a fifth control valve V5, the flow rate of chilled water to the evaporator 110 (passage) can be controlled by adjusting the opening of the fifth control valve V5 during the natural cooling mode. This adapts to changes in terminal load, further ensuring stable chilled water pressure and supply water temperature, improving system stability and adaptability, while reducing circulation resistance, lowering pump power consumption, and further optimizing energy-saving effects.

[0053] It should be noted that the three cooling modes mentioned above can be automatically switched via a controller (not shown in this document, a conventional PLC controller can be selected) based on the outdoor ambient temperature and terminal cooling load demand, or manually controlled. No shutdown is required during the switching process, and the first circulation pump 2 and the second circulation pump 3 remain running to ensure stable chilled water pressure and avoid terminal pressure fluctuations. The seamless switching between the three modes enables refined intelligent operation throughout the year, fully covering various operating conditions such as high temperature and high load, transitional seasons, and low temperature and low load. It solves the problems of high energy consumption, complex piping, large heat exchange losses, and high operation and maintenance costs of existing systems through a simple piping architecture that eliminates the need for additional plate heat exchangers and an integrated closed-loop circulation design. Furthermore, the design of continuous operation of dual circulation pumps and chilled water always flowing through the same core equipment addresses the key technical problem of unstable chilled water and terminal pressure under different operating modes. Simultaneously, the pre-cooling mode achieves synergy between natural cold source and mechanical refrigeration, solving the problems of poor adaptability to operating conditions and high compressor losses, thus balancing energy efficiency, reliability, ease of operation and maintenance, and terminal cooling stability.

[0054] Example 4 In this embodiment, the refrigeration system described above is applied to a data center 24-hour constant temperature refrigeration project. The rated total cooling load of the terminal IT equipment in this project is 800kW. The chiller unit is equipped with 2 screw chiller units, and the natural cooling equipment is equipped with 2 closed cooling towers. The standard supply and return temperature of chilled water is 15℃ / 21℃.

[0055] In summer, when the outdoor temperature exceeds 22°C, the normal cooling mode is triggered: the chiller unit operates at full load and stably.

[0056] During the spring and autumn transition season, when the outdoor temperature is 10~22℃, the pre-cooling mode is triggered: valves are linked according to their corresponding states, the natural cooling equipment pre-cools the chilled water, the chiller unit replenishes the cooling capacity at low load, and the compressor's energy consumption is reduced by 60%.

[0057] In winter, when the outdoor temperature is ≤10℃, the natural cooling mode is triggered: the chiller unit is completely shut down, the valves are linked according to the corresponding status, the pure closed tower natural cooling circulation provides cooling, and the compressor operates with zero power consumption.

[0058] Compared with the traditional dual-mode system, the system's initial investment was reduced by more than 15%, the total annual cooling energy consumption was significantly reduced, and the annual operational stability was significantly improved.

[0059] Other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the embodiments thereof. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not claimed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of this application are embodied in the appended claims.

Claims

1. A multi-mode refrigeration system based on chilled water precooling, characterized in that, include: Chiller unit, natural cooling equipment, first branch pipe, second branch pipe, first control valve, second control valve, third control valve, fourth control valve, first circulating pump and second circulating pump; among which, The chiller unit includes a condenser and an evaporator, the evaporator being connected to a chilled water outlet pipe and a chilled water return pipe; the natural cooling equipment is connected to the condenser via a cooling water outlet pipe and a cooling water return pipe. The first end of the first branch pipe, the first control valve, the first end of the second branch pipe, and the first circulating pump are sequentially connected to the chilled water return pipe along the flow direction of the chilled water; The second circulating pump, the second end of the second branch pipe, the third control valve, and the second end of the first branch pipe are sequentially connected to the cooling water outlet pipe along the flow direction of the cooling water.

2. The multi-operation mode refrigeration system according to claim 1, characterized in that, It also includes a third branch pipe, on which a fifth control valve is provided; The two ends of the third branch pipe are respectively connected to the first position and the second position of the cooling water outlet pipe. The first position is located between the second circulating pump and the second end of the second branch pipe, and the second position is located between the second end of the first branch pipe and the condenser.

3. The multi-operation mode refrigeration system according to claim 1, characterized in that, It also includes a first constant pressure water supply device, which is connected to the chilled water return pipe at a position between the first circulation pump and the first end of the second branch pipe; The second constant pressure water supply device is connected to the cooling water outlet pipe at a position between the second circulating pump and the natural cooling equipment.

4. The multi-operation mode refrigeration system according to claim 1, characterized in that, It also includes a dosing device connected to the cooling water outlet pipe at a position between the second circulating pump and the natural cooling equipment.

5. The multi-operation mode refrigeration system according to claim 1, characterized in that, It also includes a first bypass pipe, which connects the cooling water outlet pipe and the cooling water return pipe and is close to the condenser. The first bypass pipe is equipped with a control valve. The second bypass pipe connects the chilled water return pipe and the chilled water outlet pipe, and is located near the evaporator. The second bypass pipe is equipped with a control valve.

6. The multi-operation mode refrigeration system according to claim 1, characterized in that, The natural cooling device is at least one of a cooling tower or a dry cooler.

7. The multi-operation mode refrigeration system according to claim 1, characterized in that, The multi-operation mode refrigeration system also includes: At least two chilled water temperature sensors are respectively installed in the chilled water outlet pipe and the chilled water return pipe; At least three chilled water side pressure sensors are respectively installed at the chilled water outlet pipe, the chilled water return pipe and the outlet of the first circulation pump; A chilled water flow meter is installed on the chilled water outlet pipe; At least three test terminals are reserved on the chilled water side, respectively located at the chilled water outlet pipe, the chilled water return pipe, and the outlet of the first circulation pump.

8. The multi-operation mode refrigeration system according to claim 1, characterized in that, The multi-operation mode refrigeration system also includes: At least two cooling water side temperature sensors are respectively installed in the cooling water outlet pipe and the cooling water return pipe; At least three cooling water side pressure sensors are respectively installed at the cooling water outlet pipe, the cooling water return pipe and the outlet of the second circulation pump; A cooling water flow meter is installed on the cooling water outlet pipe; At least three test terminals are reserved on the cooling water side, respectively located at the cooling water outlet pipe, the cooling water return pipe, and the outlet of the second circulation pump.

9. A control method for a multi-operation mode refrigeration system based on chilled water precooling, characterized in that, For controlling the multi-operation mode refrigeration system as described in any one of claims 1 to 7 to execute at least one of the following refrigeration modes; Normal cooling mode: Open the first and third control valves, and close the second and fourth control valves; The first circulation pump controls the chilled water to enter the evaporator through the chilled water return pipe for active cooling, and then flows to the end through the chilled water outlet pipe. The cooling water is controlled by the second circulation pump to enter the condenser through the cooling water outlet pipe for heat exchange, and then returns to the natural cooling equipment through the cooling water return pipe. Pre-cooling mode; Close the first and third control valves, and open the second and fourth control valves; Chilled water from the end enters the condenser through the first branch pipe and the cooling water outlet pipe, and then enters the natural cooling equipment for pre-cooling through the cooling water return pipe; The pre-cooled chilled water is controlled by the second circulation pump to flow into the second branch pipe through the cooling water outlet pipe; The pre-cooled chilled water is controlled by the first circulation pump to enter the evaporator for active cooling through the chilled water return pipe, and after cooling, it flows to the end through the chilled water outlet pipe. Natural cooling mode; Close the first and third control valves, open the second and fourth control valves, and stop the chiller unit from operating; Chilled water from the end enters the condenser through the first branch pipe and the cooling water outlet pipe, and then enters the natural cooling equipment for refrigeration through the cooling water return pipe; The chilled water after cooling is controlled by the second circulation pump to flow into the second branch pipe through the cooling water outlet pipe; The chilled water, after being cooled, flows through the evaporator via the chilled water return pipe and then through the chilled water outlet pipe to the end via the first circulation pump.

10. The control method for a multi-operation mode refrigeration system based on chilled water precooling according to claim 9, characterized in that, The multi-operation mode refrigeration system also includes a third branch pipe, on which a fifth control valve is provided; The two ends of the third branch pipe are respectively connected to the first position and the second position of the cooling water outlet pipe. The first position is located between the second circulating pump and the second end of the second branch pipe, and the second position is located between the second end of the first branch pipe and the condenser. The process of executing the pre-cooling mode or the natural cooling mode also includes: The flow rate of chilled water to the evaporator is controlled by adjusting the opening of the fifth control valve.

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