Supercritical carbon dioxide phase change cooling data center thermal management system and control method

Abstract

This invention discloses a supercritical carbon dioxide phase change cooling data center thermal management system and control method. The invention utilizes the thermophysical property changes of supercritical carbon dioxide near its critical point, achieving high heat dissipation efficiency in a small size. It employs multi-stage energy recovery, achieving cascaded energy utilization through the synergistic effect of heat exchangers and regenerators. A phase change evaporation module solves the heat dissipation problem of high power density. A flow control module monitors server load and temperature changes in real time, providing fast response and ensuring operation within the optimal efficiency range. An adaptive control strategy minimizes temperature fluctuations while avoiding energy waste and server rack damage. It maintains stable cooling capacity under high power density and high-temperature conditions, solving the heat dissipation challenges of high-density data centers. It is suitable for high heat flux density scenarios such as AI computing centers, supercomputing centers, and 5G base stations. Its compact design also meets the cooling needs of mobile computing platforms such as shipborne and vehicle-mounted systems, offering broad market applications.

Description

Technical Field

[0001] This invention relates to data center cooling systems, specifically to a supercritical carbon dioxide phase change cooling data center thermal management system and its control method. Background Technology

[0002] Existing data center thermal management technologies employ air-cooled or water-cooled systems, which suffer from low energy efficiency, large footprint, and reliance on water resources. Air-cooled systems rely on numerous fans to force air convection, resulting in high energy consumption (approximately 40% of total data center energy consumption), high noise levels, and low heat dissipation efficiency, making them unsuitable for high power density scenarios exceeding 20kW per rack. While water-cooled systems offer stronger heat dissipation capabilities, they are susceptible to pipe corrosion and leakage risks, have high maintenance costs, and require complex water treatment systems to prevent scaling and microbial growth, exacerbating water scarcity in arid regions. Phase change cooling technologies incorporating heat pumps utilize Freon refrigerants, which possess extremely high global warming potential (GWP typically exceeding 2000) and face increasingly stringent environmental regulations. Immersion liquid cooling, on the other hand, suffers from dielectric liquid degradation, poor equipment compatibility, and difficult maintenance. More importantly, these traditional systems generally lack intelligent adjustment capabilities, failing to respond in real-time to dynamically changing heat dissipation demands, often leading to "overcooling" and significant energy waste. Furthermore, existing technologies lack sufficient precision in humidity control, easily leading to condensation or static electricity issues. Additionally, these systems typically require a large footprint, making them ill-suited to the space constraints of modular data centers and edge computing scenarios. These inherent limitations severely hinder the development of modern data centers towards high density, green technology, and intelligence.

[0003] Existing data center thermal management systems often directly release waste heat generated by servers into the environment, failing to achieve effective heat energy recovery and utilization. Traditional air-cooling systems discharge heat into the atmosphere through air conditioning, while water-cooling systems dissipate heat through cooling towers. These methods not only consume a large amount of electrical energy for heat dissipation (accounting for approximately 30-40% of the total electricity consumption of a data center), but also waste high-quality, low-grade heat sources with temperatures between 30-45°C. Particularly noteworthy is that in systems employing mechanical refrigeration, the condenser exhaust temperature is deliberately lowered to improve cooling efficiency, which further exacerbates the devaluation of waste heat quality, making the cascade utilization of thermal energy extremely difficult.

[0004] Carbon dioxide, as a natural working fluid, has a global warming potential (GWP) of only 1, far lower than commonly used HFC refrigerants. The system does not produce any ozone-depleting substances during operation, and there is no risk of leakage as with traditional refrigerants. The entire cycle is completely closed, with no wastewater discharge, meeting the most stringent environmental standards. Furthermore, transcritical carbon dioxide systems have a high energy efficiency ratio, and due to their superior thermodynamic properties, they can complete the refrigeration process with relatively low energy input. Compared to traditional refrigerants, carbon dioxide systems operate at relatively lower pressures, which reduces equipment wear and extends system lifespan; they also exhibit high heat exchange efficiency in the transcritical range, maintaining good refrigeration performance even at high temperatures. Supercritical carbon dioxide (sCO2), due to its high thermal conductivity, low viscosity, and environmentally friendly characteristics, has become an ideal choice for new cooling working fluids. However, existing sCO2 cooling systems still have room for improvement in phase change control, flow regulation, and humidity management. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention proposes a supercritical carbon dioxide phase change cooling data center thermal management system and its control method. By optimizing the circulation structure and combining phase change evaporation modules and intelligent flow control, this invention significantly improves heat dissipation efficiency and adaptability, greatly enhances energy utilization efficiency, and transforms the data center from a mere energy consumer into a component of the regional energy network.

[0006] One objective of this invention is to provide a supercritical carbon dioxide phase change cooling data center thermal management system.

[0007] The supercritical carbon dioxide phase change cooling data center thermal management system of the present invention includes: a compressor unit, a heat exchanger, a regenerator, a throttling device, first and second gas-liquid separators, a flow control valve, a phase change evaporation module, and a flow control module; wherein, the gas phase outlet of the regenerator is connected to the low-pressure side of the compressor unit, and the high-pressure side of the compressor unit is connected to the CO2 inlet of the heat exchanger; the CO2 outlet of the heat exchanger is connected to the supercritical inlet of the regenerator, the supercritical inlet and supercritical outlet of the regenerator are internally connected through a supercritical pipe, and the supercritical outlet of the regenerator is connected to the gas-liquid two-phase inlet of the first gas-liquid separator through the throttling device; the first... The gas phase outlet of the first gas-liquid separator is connected to the gas-liquid two-phase inlet of the second gas-liquid separator; the liquid phase outlet of the first gas-liquid separator is connected to the inlet of the phase change evaporation module through a flow control valve. The phase change evaporation module is located in the server rack of the data center computer room; the outlet of the phase change evaporation module is connected to the gas-liquid two-phase inlet of the second gas-liquid separator, and the liquid phase outlet of the second gas-liquid separator is connected before the inlet of the phase change evaporation module; the gas phase outlet of the second gas-liquid separator is connected to the gas phase inlet of the regenerator. The gas phase outlet and the gas phase inlet of the regenerator are connected internally through a gas phase pipeline, but the gas phase pipeline of the regenerator is not connected to the supercritical pipeline.

[0008] The flow control module is connected to the control terminals of the flow control valve and the compressor unit, respectively; the temperature sensor and hardware performance sensor installed in the server rack in the data center are connected to the flow control module, respectively.

[0009] Furthermore, the present invention also includes an oil separator, which is installed between the high-pressure side of the compressor unit and the heat exchanger. After passing through the compressor unit, the supercritical carbon dioxide (sCO2) that becomes high temperature and high pressure passes through the oil separator to separate the lubricating oil in the compressor unit from the CO2, so as to avoid affecting the subsequent fluid flow and heat exchange process.

[0010] The compressor unit uses multiple compressors connected in parallel.

[0011] The heat exchanger is a heat recovery heat exchanger. The inlet and outlet of the heat transfer medium are connected to the external heat-consuming end, which is used for heating industrial or domestic water or for building space heating. The inlet and outlet of the heat transfer medium are connected by a heat transfer medium pipe, and the heat transfer medium flows inside the heat transfer medium pipe. The heat transfer medium can be water or air. The inlet and outlet of CO2 are connected by a CO2 pipe, and CO2 flows inside the CO2 pipe. The heat transfer medium pipe and the CO2 pipe are not connected. Inside the heat recovery heat exchanger, the CO2 inlet and outlet are in the opposite direction to the heat transfer medium inlet and outlet. The flow direction of CO2 is opposite to the flow direction of the heat transfer medium inside the heat recovery heat exchanger. The heat exchange between CO2 and the heat transfer medium is a counter-current heat exchange method, which makes good use of the heat of the data center with the external heat-consuming end.

[0012] The throttling device can be a fixed throttling device, an adjustable flow device, an electronic throttling device, an intelligent throttling device, a multi-hole plug throttling device, or a labyrinth throttling device.

[0013] The phase change evaporation module consists of multiple sets of evaporators connected in parallel, with each evaporator mounted in a server rack in the data center computer room.

[0014] The flow control module uses a microcontroller, host computer, programmable logic controller (PLC), or industrial computer. Based on the CPU and GPU utilization rates and the temperature inside the server rack, the flow control module dynamically adjusts the CO2 flow rate entering the phase change evaporation module and the CO2 flow rate at the compressor unit outlet.

[0015] The flow control module receives performance monitoring signals from the integrated hardware performance counters of the Central Processing Unit (CPU) (such as Intel's PCU (Power Control Unit) or AMD's SMU (System Management Unit)) and the performance sensors of the Graphics Processing Unit (GPU) (such as NVIDIA's NVAPI (NVIDIA Application Programming Interface)) to obtain the CPU and GPU utilization rates. It also receives temperature signals from temperature sensors connected inside and outside the server rack, or from the CPU's built-in Digital Thermal Sensor (DTS), to monitor the temperature inside the server rack. These temperature sensors collect temperature data from the chip surface or the inlet and outlet temperatures of the phase change evaporation module (used to detect phase changes). Based on the temperature inside the server rack and the CPU and GPU utilization rates, or solely based on the temperature inside the server rack, the flow control module determines the CO2 flow rate and the number of compressors operating. The flow control module controls the switching on and off of each compressor in the compressor unit, the load on each compressor, and dynamically adjusts the flow rate of liquid CO2 passing through the flow control valve.

[0016] Another objective of this invention is to propose a control method for a supercritical carbon dioxide phase change cooling data center thermal management system.

[0017] The control method of the supercritical carbon dioxide phase change cooling data center thermal management system of the present invention includes the following steps:

[0018] 1) Gas CO2 from the gas phase pipe of the regenerator enters the compressor unit, where it is pressurized and heated to become high-temperature and high-pressure supercritical carbon dioxide sCO2, which has high density and high heat capacity, and the high-pressure side temperature and pressure of the compressor unit are increased.

[0019] 2) Carbon dioxide is transferred to the heat exchanger, which then transfers the heat extracted by the thermal management system to the outside for initial cooling, reducing the CO2 temperature but still maintaining it in a supercritical state, thereby improving energy efficiency.

[0020] 3) After heat exchange, the sCO2 enters the supercritical pipe of the regenerator and exchanges heat with the gaseous CO2 returning from the gas phase pipe, further cooling down while still maintaining the supercritical state and at an even lower temperature; the synergistic effect of the heat exchanger and the regenerator realizes the cascade utilization of energy.

[0021] 4) Low-temperature sCO2 flows through the throttling device, where the sCO2 is depressurized to the subcritical region, and some of the CO2 liquefies, forming a gas-liquid two-phase state.

[0022] 5) After passing through the throttling device, the two-phase CO2 enters the first gas-liquid separator. The liquid phase CO2 is separated and settled and then transferred to the phase change evaporation module via the flow control valve. The gas phase CO2 rises and is transferred to the second gas-liquid separator, where the liquid and gas phases of CO2 are separated.

[0023] 6) The flow control module monitors the data center occupancy rate and temperature changes in the server rack in real time. Based on the occupancy rate and temperature, or only based on the temperature in the server rack, it precisely controls the flow control valve to dynamically adjust the flow rate of liquid CO2 to ensure evaporation efficiency and transmits the data to the phase change evaporation module.

[0024] 7) The phase change evaporation module absorbs heat through the evaporation of liquid CO2 to cool the server, turning it into gaseous CO2. After cooling, the gaseous CO2 mixed with a small amount of liquid CO2 is transferred to the second gas-liquid separator.

[0025] 8) The second gas-liquid separator separates gaseous CO2 and liquid CO2, and sends liquid CO2 back to the inlet of the phase change evaporation module, while gaseous CO2 is transferred to the gas phase pipeline of the regenerator.

[0026] 9) The gaseous CO2 in the gas phase pipe of the regenerator exchanges heat with the sCO2 in the supercritical pipe. After being preheated, it returns to the compressor to complete the closed-loop cycle.

[0027] In step 1), the compressor compresses the carbon dioxide working fluid to a supercritical state: pressure > 7.38 MPa, temperature > 31.1 °C. The flow control module controls the switching on and off of each compressor in the compressor unit and the load on each compressor.

[0028] Before entering the heat exchanger, the supercritical CO2, which becomes high temperature and high pressure after passing through the compressor unit, passes through an oil separator to separate the lubricating oil in the compressor unit from the CO2, so as to avoid affecting the subsequent fluid flow and heat exchange process.

[0029] In step 2), the heat exchanger is a heat recovery heat exchanger connected to the external heat-using end; the external heat-using end is for heating industrial or domestic water or for heating building space; the heat exchange between sCO2 and the heat transfer medium of the external heat-using end is a counter-current heat exchange method. The efficient counter-current heat exchange method is used to recover the residual cold energy of the low-temperature gas phase CO2 returned from the phase change heat dissipation module, which is used to pre-cool the CO2 that is about to enter the throttling device. The external heat-using end makes good use of the heat of the data center. By lowering the working fluid temperature before throttling, reducing the proportion of flash gas after throttling, and minimizing irreversible losses during the throttling process, the system's coefficient of performance (COP) is improved. It also ensures that the working fluid entering the compressor is a moderately superheated pure gas, preventing liquid working fluid from entering the compressor and causing liquid slugging (i.e., mechanical damage risk). The heat recovery heat exchanger recovers the residual cold energy of the low-temperature gaseous CO2 returned from the phase change evaporation module, which is used to pre-cool the CO2 about to enter the throttling device, lowering the working fluid temperature before throttling, reducing the proportion of flash gas after throttling, minimizing irreversible losses during the throttling process, and improving the system's COP. It also ensures that the working fluid entering the compressor is a moderately superheated pure gas, preventing liquid CO2 from entering the compressor and causing liquid slugging (i.e., mechanical damage risk). Furthermore, the heat recovery heat exchanger extracts waste heat from data center server rooms for urban building heating or industrial or domestic water heating.

[0030] In step 4), the throttling device reduces the CO2 pressure by 3-5 MPa.

[0031] In step 6), the integrated hardware performance counter transmits the CPU utilization rate, and the performance sensor transmits the PCU utilization rate to the flow control module. The temperature sensor transmits the temperature inside the server rack, and the flow control module obtains the CPU and PCU utilization rates as well as the temperature inside the server rack. The thermal management system of this invention is equipped with high-precision temperature sensors and hardware performance sensors in the data center rack. The flow control module controls a fast-response flow control valve, adjusting the CO2 flow rate in seconds based on the temperature distribution inside the server rack and the CPU and PCU utilization rates. When the temperature is too high, the flow control module immediately increases the CO2 flow rate to ensure sufficient liquid CO2 participates in the phase change heat absorption. When the temperature is low, the CO2 flow rate is automatically reduced to reduce energy consumption. When a sudden increase in CPU or GPU utilization is detected, the flow rate is increased in advance to prevent temperature spikes. This intelligent adjustment mechanism not only avoids the common overcooling or overheating problems of traditional cooling systems but also ensures that the system always operates at its optimal efficiency point, while controlling temperature fluctuations within ±2℃.

[0032] Advantages of this invention:

[0033] (1) Make full use of the special thermophysical property changes of supercritical carbon dioxide near the critical point (31.1℃, 7.38MPa), exhibiting extremely high heat transfer coefficient (up to 3 to 5 times that of water) and significant heat capacity change characteristics in the near-critical region. The required heat exchanger volume is greatly reduced, only about 1 / 3 of that of the traditional water cooling system, but the heat dissipation capacity is increased by 50%. This unique physical property enables the thermal management system to achieve extremely high heat dissipation efficiency.

[0034] (2) A multi-stage energy recovery architecture is adopted, and the energy is utilized in stages through the synergistic effect of heat exchangers and regenerators; the phase change evaporation module effectively solves the problem of heat dissipation at high power density.

[0035] (3) The thermal management system is equipped with a flow control module to monitor the server CPU / GPU load and temperature changes in real time, and dynamically adjust the CO2 flow with a response speed of seconds to ensure that the thermal management system always works in the optimal efficiency range. This adaptive control strategy keeps the temperature fluctuation within ±2℃, while avoiding energy waste and server rack damage caused by "overcooling".

[0036] (4) It uses natural working fluid CO2 (GWP=1, ODP=0), which is completely free of harmful substances such as Freon. The thermal management system has a fully enclosed circulation design to achieve zero wastewater discharge and extremely low operating noise, which ensures the stability of the cooling effect and maximizes the energy utilization efficiency of the system. Compared with traditional refrigerants, carbon emissions are reduced by more than 60%, which fully complies with the most stringent environmental protection regulations.

[0037] (5) The modular design makes the thermal management system have a small footprint and high power density per rack; the high power density makes the system flexible to be deployed in data centers of various sizes, especially for modular data centers and edge computing nodes; the standardized interface design facilitates installation and maintenance and supports flexible plug-and-play replacement of components; the thermal management system can operate stably in an ambient temperature range of 0 to 120°C, which is particularly suitable for harsh environments such as edge computing; sCO2 not only has a higher specific heat capacity and thermal conductivity, but also a more prominent latent heat of phase change. Even when the chip is operating at a high temperature of over 80°C, the system can still maintain stable cooling capacity, providing a new solution to the heat dissipation problem of high-density data centers;

[0038] (6) In addition to traditional data centers, thermal management systems are particularly suitable for high heat flux density scenarios such as artificial intelligence (AI) computing centers, supercomputing centers and 5G base stations; they adopt a modular design, and the components can be flexibly deployed and combined like building blocks, which is convenient for expansion or adjustment according to actual needs; their compact design is also suitable for the cooling needs of mobile computing platforms such as shipborne and vehicle-mounted platforms, and has a broad market application space. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of an embodiment of the supercritical carbon dioxide phase change cooling data center thermal management system of the present invention. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0041] like Figure 1 As shown, the supercritical carbon dioxide phase change cooling data center thermal management system of this embodiment includes: a compressor unit, an oil separator, a heat exchanger, a regenerator, a throttling device, first and second gas-liquid separators, a flow control valve, a phase change evaporation module, and a flow control module; wherein, the gas phase outlet of the regenerator is connected to the low-pressure side of the compressor unit, and the high-pressure side of the compressor unit is connected to the CO2 inlet of the heat exchanger through the oil separator; the heat exchanger is a heat recovery heat exchanger, and the heat transfer medium inlet and outlet of the heat recovery heat exchanger are respectively connected to the external heat-using end; The external heat-using end is for heating industrial or domestic water or providing heating for building spaces. The inlet and outlet of the heat transfer medium are connected via a heat transfer medium pipeline, within which the heat transfer medium flows. The heat transfer medium can be water or air. The inlet and outlet of the CO2 are connected via a CO2 pipeline, within which CO2 flows. The heat transfer medium pipeline and the CO2 pipeline are not connected. Within the heat recovery heat exchanger, the positions of the CO2 inlet and outlet are opposite to those of the heat transfer medium inlet and outlet. The flow direction of CO2 is opposite to the flow direction of the heat transfer medium. The heat exchanger operates in a counter-current manner, where CO2 exchanges heat with the heat transfer medium in a counter-current fashion. The CO2 outlet of the heat exchanger is connected to the supercritical inlet of the regenerator. The supercritical inlet and outlet of the regenerator are internally connected via a supercritical pipe. The supercritical outlet of the regenerator is connected to the gas-liquid two-phase inlet of the first gas-liquid separator via a throttling device. The gas phase outlet of the first gas-liquid separator is connected to the gas-liquid two-phase inlet of the second gas-liquid separator. The liquid phase outlet of the first gas-liquid separator is connected to the phase change evaporation module via a flow control valve. The inlet and throttling device adopt an adjustable flow device. The phase change evaporation module includes multiple sets of evaporators connected in parallel. Each evaporator is mounted in each server rack in the data center computer room. The outlet of the phase change evaporation module is connected to the gas-liquid two-phase inlet of the second gas-liquid separator. The liquid phase outlet of the second gas-liquid separator is connected to the inlet of the phase change evaporation module. The gas phase outlet of the second gas-liquid separator is connected to the gas phase inlet of the regenerator. The gas phase outlet and the gas phase inlet of the regenerator are connected through a gas phase pipeline. The gas phase pipeline of the regenerator is not connected to the supercritical pipeline.

[0042] The flow control module uses a microcontroller, which is connected to the control terminals of the flow control valve and the compressor unit respectively; the temperature sensor and hardware performance sensor installed in the server rack in the data center are connected to the flow control module respectively.

[0043] The control method of the supercritical carbon dioxide phase change cooling data center thermal management system in this embodiment includes the following steps:

[0044] 1) Gas-phase CO2 from the gas phase pipe of the regenerator enters multiple parallel compressors, where it is pressurized and heated to become high-temperature and high-pressure supercritical carbon dioxide (sCO2) with a temperature of 55-85℃ and a pressure greater than 7.38MPa. It has high density and high heat capacity, and the high-pressure side temperature and pressure of the compressor unit are increased. After passing through the compressor unit, the high-temperature and high-pressure supercritical CO2 passes through an oil separator to separate the lubricating oil in the compressor unit from the CO2, so as to avoid affecting the subsequent fluid flow and heat exchange process.

[0045] 2) Carbon dioxide is transferred to the heat recovery heat exchanger, which provides the heat extracted by the thermal management system to the outside. The heat of the data center is properly utilized by the external heat-using end. The carbon dioxide exchanges heat with the heat transfer medium through a counter-current heat exchange method, which performs preliminary cooling, reduces the temperature of the carbon dioxide, but still maintains the supercritical state, thus improving energy efficiency.

[0046] 3) After heat exchange, the sCO2 enters the supercritical pipe of the regenerator and exchanges heat with the gaseous CO2 returning from the gas phase pipe, further cooling it down while maintaining the supercritical state and at an even lower temperature (but not lower than 33°C); the synergistic effect of the heat exchanger and the regenerator realizes the cascade utilization of energy.

[0047] 4) Low-temperature sCO2 flows through a throttling device, where the sCO2 pressure drops to a sudden subcritical region of 3-5 MPa, and some of the CO2...

[0048] Liquefaction occurs, forming a two-phase gas-liquid state.

[0049] 5) After passing through the throttling device, the two-phase CO2 enters the first gas-liquid separator. The liquid phase CO2 is separated and settled and then transferred to the phase change evaporation module via the flow control valve. The gas phase CO2 rises and is transferred to the second gas-liquid separator, where the liquid and gas phases of CO2 are separated.

[0050] 6) The flow control module monitors in real time. It receives performance monitoring signals from the CPU's integrated hardware performance counter and the GPU's performance sensor to obtain the CPU and GPU utilization rates. It also collects data from temperature sensors connected inside and outside the server rack, or from the CPU's built-in DTS, to monitor the temperature inside the server rack and obtain the chip surface temperature or the inlet and outlet temperatures of the phase change evaporation module. The integrated hardware performance counter transmits the CPU utilization rate, and the performance sensor transmits the PCU utilization rate to the flow control module. The temperature sensor transmits the server rack temperature, allowing the flow control module to obtain the CPU and PCU utilization rates and the server rack temperature. Based on the temperature distribution inside the server rack, the CPU and PCU utilization rates, and other parameters, the flow control module adjusts the CO2... It performs flow rate adjustments in seconds; when the data center load suddenly increases, the flow control module detects the temperature increase in real time through temperature sensors, and immediately increases the CO2 flow rate to ensure that there is enough liquid CO2 to participate in the phase change heat absorption; when the temperature is low, it automatically reduces the CO2 flow rate to reduce energy consumption; when the flow control module detects a sudden increase in CPU or GPU utilization, it increases the flow rate in advance to avoid temperature spikes; this intelligent adjustment mechanism not only avoids the overcooling or overheating problems common in traditional cooling systems, but also ensures that the system always works at its optimal efficiency point, while keeping temperature (rack air temperature 20-45℃, CPU core temperature 30-85℃, GPU core temperature 35-95℃, TPU core temperature 45-100℃) fluctuations within ±2℃;

[0051] 7) The phase change evaporation module absorbs heat through the evaporation of liquid CO2 to cool the server, turning it into gaseous CO2. After cooling, the gaseous CO2 mixed with a small amount of liquid CO2 is transferred to the second gas-liquid separator.

[0052] 8) The second gas-liquid separator separates gaseous CO2 and liquid CO2, and sends liquid CO2 back to the inlet of the phase change evaporation module, while gaseous CO2 is transferred to the gas phase pipeline of the regenerator.

[0053] 9) The gaseous CO2 in the gas phase pipe of the regenerator exchanges heat with the sCO2 in the supercritical pipe. After being preheated, it returns to the compressor to complete the closed-loop cycle. This closed-loop design not only ensures the stability of the cooling effect, but also maximizes the energy utilization efficiency of the system.

[0054] Finally, it should be noted that the purpose of disclosing the embodiments is to help further understand the present invention. However, those skilled in the art will understand that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the scope of protection of the present invention is defined by the claims.

Claims

1. A supercritical carbon dioxide phase change cooling data center thermal management system, characterized in that, The data center thermal management system includes: a compressor unit, a heat exchanger, a regenerator, a throttling device, first and second gas-liquid separators, a flow control valve, a phase change evaporation module, and a flow control module. The gas phase outlet of the regenerator is connected to the low-pressure side of the compressor unit, and the high-pressure side of the compressor unit is connected to the CO2 inlet of the heat exchanger. The CO2 outlet of the heat exchanger is connected to the supercritical inlet of the regenerator. The supercritical inlet and supercritical outlet of the regenerator are internally connected via a supercritical pipe. The supercritical outlet of the regenerator is connected to the gas-liquid two-phase inlet of the first gas-liquid separator via a throttling device. The first gas-liquid separator... The gas phase outlet is connected to the gas-liquid two-phase inlet of the second gas-liquid separator; the liquid phase outlet of the first gas-liquid separator is connected to the inlet of the phase change evaporation module via a flow control valve. The phase change evaporation module is located inside the server rack of the data center computer room; the outlet of the phase change evaporation module is connected to the gas-liquid two-phase inlet of the second gas-liquid separator, and the liquid phase outlet of the second gas-liquid separator is connected before the inlet of the phase change evaporation module; the gas phase outlet of the second gas-liquid separator is connected to the gas phase inlet of the regenerator. The gas phase outlet and the gas phase inlet of the regenerator are connected internally via a gas phase pipe, but the gas phase pipe of the regenerator is not connected to the supercritical pipe. The flow control module is connected to the control terminals of the flow control valve and the compressor unit, respectively; the temperature sensor and hardware performance sensor installed in the server rack in the data center are connected to the flow control module, respectively.

2. The data center thermal management system as described in claim 1, characterized in that, It also includes an oil separator, which is installed between the high-pressure side of the compressor unit and the heat exchanger. After passing through the compressor unit, the supercritical carbon dioxide (sCO2) that becomes high temperature and high pressure passes through the oil separator to separate the lubricating oil in the compressor unit from the CO2.

3. The data center thermal management system as described in claim 1, characterized in that, The compressor unit uses multiple compressors connected in parallel.

4. The data center thermal management system as described in claim 1, characterized in that, The heat exchanger is a heat recovery heat exchanger. The inlet and outlet of the heat transfer medium are connected to an external heat-consuming end, which is used for heating industrial or domestic water or for building space heating. The inlet and outlet of the heat transfer medium are connected by a heat transfer medium pipe, and the heat transfer medium flows inside the heat transfer medium pipe. The heat transfer medium is water or air. The inlet and outlet of CO2 are connected by a CO2 pipe, and CO2 flows inside the CO2 pipe. The heat transfer medium pipe and the CO2 pipe are not connected. Inside the heat recovery heat exchanger, the positions of the CO2 inlet and outlet are opposite to those of the heat transfer medium inlet and outlet. The flow direction of CO2 is opposite to the flow direction of the heat transfer medium inside the heat recovery heat exchanger. The heat exchange between CO2 and the heat transfer medium is a counter-current heat exchange method.

5. The data center thermal management system as described in claim 1, characterized in that, The throttling device can be a fixed throttling device, an adjustable throttling device, an electronic throttling device, an intelligent throttling device, a multi-hole plug-type throttling device, or a labyrinth-type throttling device.

6. The data center thermal management system as described in claim 1, characterized in that, The phase change evaporation module includes multiple sets of evaporators connected in parallel, with each evaporator mounted in a server rack in the data center computer room.

7. The data center thermal management system as described in claim 1, characterized in that, The flow control module uses a microcontroller, host computer, programmable logic controller or industrial control computer.

8. A control method for a supercritical carbon dioxide phase change cooling data center thermal management system as described in claim 1, characterized in that, The control method includes the following steps: 1) Gas CO2 from the gas phase pipe of the regenerator enters the compressor unit, where it is pressurized and heated to become high-temperature and high-pressure supercritical carbon dioxide sCO2, which has high density and high heat capacity, and the high-pressure side temperature and pressure of the compressor unit are increased. 2) Carbon dioxide is transferred to the heat exchanger, which then transfers the heat extracted by the thermal management system to the outside for initial cooling. Lowering the sCO2 temperature while maintaining a supercritical state improves energy efficiency; 3) After heat exchange, the sCO2 enters the supercritical pipe of the regenerator and exchanges heat with the gaseous CO2 returning from the gas phase pipe, further cooling down while still maintaining the supercritical state and at an even lower temperature; the synergistic effect of the heat exchanger and the regenerator realizes the cascade utilization of energy. 4) Low-temperature sCO2 flows through the throttling device, where the sCO2 is depressurized to the subcritical region, and some of the CO2 liquefies, forming a gas-liquid two-phase state. 5) After passing through the throttling device, the two-phase CO2 enters the first gas-liquid separator. The liquid phase CO2 is separated and settled and then transferred to the phase change evaporation module via the flow control valve. The gas phase CO2 rises and is transferred to the second gas-liquid separator, where the liquid and gas phases of CO2 are separated. 6) The flow control module monitors the data center occupancy rate and temperature changes in the server rack in real time. Based on the occupancy rate and temperature, or only based on the temperature in the server rack, it precisely controls the flow control valve to dynamically adjust the flow rate of liquid CO2 to ensure evaporation efficiency and transmits the data to the phase change evaporation module. 7) The phase change evaporation module absorbs heat through the evaporation of liquid CO2 to cool the server, turning it into gaseous CO2. After cooling, the gaseous CO2 mixed with a small amount of liquid CO2 is transferred to the second gas-liquid separator. 8) The second gas-liquid separator separates gaseous CO2 and liquid CO2, and sends liquid CO2 back to the inlet of the phase change evaporation module, while gaseous CO2 is transferred to the gas phase pipeline of the regenerator. 9) The gaseous CO2 in the gas phase pipe of the regenerator exchanges heat with the sCO2 in the supercritical pipe. After being preheated, it returns to the compressor to complete the closed-loop cycle.

9. The control method as described in claim 8, characterized in that, In step 2), the heat exchanger is a heat recovery heat exchanger connected to the external heat-using end; the external heat-using end is for heating industrial or domestic water or for heating building space; the heat exchange between sCO2 and the heat transfer medium of the external heat-using end is a counter-current heat exchange method.

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