High-pressure-ratio high-efficiency magnetic suspension centrifugal high-temperature heat pump system

Abstract

The invention discloses a high-pressure-ratio high-efficiency magnetic suspension centrifugal high-temperature heat pump system which takes an environment-friendly refrigerant R1234ze (E) as a working medium, a magnetic suspension centrifugal compressor is provided with a main air suction port and an air supply enthalpy increasing port, and a refrigerant side outlet pipeline of a condenser is divided into a main pipeline and a branch pipeline; the main path is sequentially connected with the condensation side of the economizer, the first electronic expansion valve and a refrigerant inlet of the evaporator, a refrigerant outlet of the evaporator is connected to a main air suction port of the magnetic suspension centrifugal compressor, the branch path is connected with an inlet of the second electronic expansion valve, and an outlet of the second electronic expansion valve is connected with a hot side inlet of the economizer. According to the system, through innovative integration of the magnetic suspension centrifugal compressor, the economizer air supply circulation and a multivariable cooperative control system, the technical problems are effectively solved, and high-temperature hot water of 90 DEG C or above can be efficiently, stably and safely produced under the ultrahigh compression ratio.

Description

Technical Field

[0001] This invention relates to the fields of heat pump technology and industrial energy-saving technology, specifically to a high-pressure-ratio, high-efficiency magnetic levitation centrifugal high-temperature heat pump system. Background Technology

[0002] In industrial sectors (such as food processing, electroplating, slaughtering, and textile printing and dyeing), many processes require high-temperature hot water at around 90°C. Currently, this heat energy is typically provided by gas-fired boilers, electric boilers, or steam, which results in high energy consumption, large carbon emissions, and expensive operating costs.

[0003] Heat pump technology is a highly efficient solution for transferring heat energy, but its application has long been limited to the medium and low temperature range. Expanding into the high temperature field faces core technological challenges: First, the increase in condensing temperature leads to a sharp increase in the system compression ratio (pressure ratio ≥ 6), which puts extreme demands on the performance, reliability, and efficiency of the compressor; Second, traditional scroll or piston compressors suffer severe efficiency degradation at high pressure ratios, and the exhaust temperature is too high, affecting system life and safety; Third, commonly used refrigerants such as R134a may face environmental regulations due to excessively high GWP values, or have poor thermodynamic performance under high temperature conditions.

[0004] Magnetic levitation centrifugal compressors possess inherent advantages such as high speed, oil-free lubrication, low friction loss, and wide adjustment range, making them ideal for high compression ratio applications. Environmentally friendly refrigerant R1234ze(E) boasts zero ODP and extremely low GWP, making it an ideal working fluid for future high-temperature heat pumps. However, combining magnetic levitation centrifugal technology, R1234ze(E) working fluid, and economizer cycles in heat pump systems with high pressure ratios and high outlet water temperatures still requires overcoming a series of technical challenges, including system optimization design, surge protection, and transient process control, to fully realize its potential for high efficiency, stability, and reliability.

[0005] The existing high-temperature heat pump system has the following technical problems: (1) Under high-temperature conditions with a pressure ratio ≥6, the traditional compressor has low efficiency, poor reliability, and excessively high exhaust temperature; (2) Under transient conditions such as startup and low load, the centrifugal compressor is prone to surge and there is a risk of liquid slugging, which affects stability and lifespan; (3) There is a lack of integrated intelligent control strategy that matches the magnetic levitation centrifugal compressor and the gas replenishment cycle, which makes it impossible for the system to always tend to the optimal operation; (4) The use of high GWP refrigerant has poor environmental performance. Summary of the Invention

[0006] The purpose of this invention is to provide a high-pressure-ratio, high-efficiency magnetic levitation centrifugal high-temperature heat pump system. This system effectively solves the above-mentioned technical problems through the innovative integration of a magnetic levitation centrifugal compressor, an economizer gas replenishment circulation, and a multi-variable collaborative control system, and achieves efficient, stable, and safe production of high-temperature hot water above 90°C under ultra-high compression ratio.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a high-pressure-ratio, high-efficiency magnetic levitation centrifugal high-temperature heat pump system, comprising a magnetic levitation centrifugal compressor, a condenser, a first electronic expansion valve, an economizer, a second electronic expansion valve, an evaporator, and a control system. The high-temperature heat pump system uses environmentally friendly refrigerant R1234ze(E) as the working fluid. The magnetic levitation centrifugal compressor is provided with a main suction port and a gas injection enthalpy-increasing port. The refrigerant-side outlet pipeline of the condenser is divided into a main line and a branch line. The main line is sequentially connected to the condenser side of the economizer, the first electronic expansion valve, and the refrigerant inlet of the evaporator. The refrigerant outlet of the evaporator is connected to the main suction port of the magnetic levitation centrifugal compressor. The branch line is connected to the inlet of the second electronic expansion valve. The outlet of the second electronic expansion valve is connected to the hot-side inlet of the economizer. The hot-side outlet of the economizer is connected to the gas injection enthalpy-increasing port of the magnetic levitation centrifugal compressor. The control system is communicatively connected to the magnetic levitation centrifugal compressor, the first electronic expansion valve, and the second electronic expansion valve. The control system is configured to perform the following operations: The rotational speed of the magnetic levitation centrifugal compressor is adjusted based on the condenser outlet water temperature; The opening of the second electronic expansion valve is adjusted based on the superheat of the compressor's exhaust gas. The opening degree of the first electronic expansion valve is adjusted based on the superheat at the evaporator outlet.

[0008] Furthermore, it also includes a third electronic expansion valve connected between the condenser and the evaporator.

[0009] Furthermore, the third electronic expansion valve is used to prevent surge of the magnetically levitated centrifugal compressor and / or to protect the compressor from liquid slugging during system startup.

[0010] Furthermore, the magnetic levitation centrifugal compressor is a single-stage compressor with an operating speed of 20,000-50,000 rpm, and can achieve a pressure ratio greater than or equal to 6.

[0011] Furthermore, the condenser is a shell-and-tube heat exchanger or a plate heat exchanger, and its water channel outlet outputs high-temperature process hot water with a temperature greater than or equal to 90°C.

[0012] Furthermore, the water channel of the evaporator is connected to a low-temperature wastewater, geothermal tailwater, or ambient air source, with a heat source temperature range of 10°C to 40°C.

[0013] Furthermore, the control system is also communicatively connected to a third electronic expansion valve and is configured to control the opening of the third electronic expansion valve to establish a pressure differential and / or prevent surge during system startup or low-load conditions.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. The high-speed magnetic levitation centrifugal compressor has a wide speed regulation characteristic, which helps to match the high pressure ratio requirements. At the same time, it innovatively integrates an economizer injection enthalpy-increasing cycle and uses a second electronic expansion valve to control the injection, thereby achieving intermediate cooling of the compression process. This helps to reduce the exhaust temperature and reduce the compression work, so that the single-stage system has the potential to achieve a higher COP (e.g., 4.5 or higher under certain operating conditions) when the pressure ratio is ≥6. 2. In view of the potential risks of surge and liquid slugging in centrifugal compressors, this invention adds a bypass protection circuit composed of a third electronic expansion valve. Its control strategy can help balance the pressure difference to achieve low-load start-up during startup, and intervene at low load to help prevent surge, thereby helping to enhance the operational stability and service life of the system. 3. The hierarchical intelligent control system combines water temperature control, superheat control and safety protection control, enabling the system to make relatively fast and accurate coordinated responses to changes in operating conditions. This helps the system to move towards a better operating state and achieve on-demand output and high-efficiency energy-saving operation. 4. Significant environmental and economic benefits: Using R1234ze(E) refrigerant with ODP=0 and low GWP value, the system can raise low-grade waste heat to above 90°C for use. Compared with traditional boilers, it has the potential to achieve significant energy savings (e.g., energy saving rate may reach 70% or higher) and reduce operating costs. The investment payback period is relatively short, and it has good economic and environmental benefits. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the principle of the high-pressure-ratio, high-efficiency magnetic levitation centrifugal high-temperature heat pump system of the present invention.

[0016] In the attached diagram, the following are the reference numerals: 1. Magnetic levitation centrifugal compressor; 2. Condenser; 3. First electronic expansion valve; 4. Economizer; 5. Second electronic expansion valve; 6. Evaporator; 7. Third electronic expansion valve. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Identical components are denoted by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, while the terms "bottom" and "top," "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0018] like Figure 1As shown, the present invention provides a technical solution: a high-pressure-ratio, high-efficiency magnetic levitation centrifugal high-temperature heat pump system, including a magnetic levitation centrifugal compressor 1, a condenser 2, a first electronic expansion valve 3, an economizer 4, a second electronic expansion valve 5, an evaporator 6, and a control system. The condenser 2 is a shell-and-tube heat exchanger. The high-temperature heat pump system uses environmentally friendly refrigerant R1234ze(E) as the working fluid.

[0019] The magnetic levitation centrifugal compressor 1 is equipped with a main suction port and a gas replenishment and enthalpy increase port. The refrigerant side outlet of the condenser 2 is divided into a main line and a branch line through a three-way fitting.

[0020] The control system uses electrical signal lines (such as...) Figure 1 (As shown by the dashed line) It is communicatively connected to the magnetic levitation centrifugal compressor 1, the first electronic expansion valve 3, the second electronic expansion valve 5 and the third electronic expansion valve 7 to form a closed-loop control.

[0021] The connection and flow of the main circuit are as follows: The high-temperature and high-pressure liquid refrigerant flowing out from the condenser 2 first enters the condenser side of the economizer 4, releases sensible heat and is further subcooled; then it flows through the first electronic expansion valve 3 for throttling and pressure reduction, becoming a low-temperature and low-pressure gas-liquid two-phase mixture; then it enters the refrigerant side of the evaporator 6, absorbs heat from the low-grade heat source (such as wastewater) in its water circuit, and after complete evaporation and superheating, forms a low-temperature and low-pressure superheated vapor; finally, the superheated vapor returns to the main suction port of the magnetic levitation centrifugal compressor 1 through the pipeline, completing the main circulation loop.

[0022] The connection and flow of the branch circuit are as follows: Part of the liquid refrigerant flowing out from the condenser 2 flows through the second electronic expansion valve 5 for throttling and pressure reduction, becoming a medium-temperature and medium-pressure gas-liquid two-phase mixture; then it enters the hot side of the economizer 4, absorbs heat from the main refrigerant and evaporates completely, becoming a medium-temperature and medium-pressure saturated or superheated gas; finally, this gas enters the intermediate pressure section of the compression chamber through the pipeline from the gas injection and enthalpy increase port of the magnetic levitation centrifugal compressor 1, mixes with the main refrigerant vapor that is being compressed, and completes the gas injection and enthalpy increase cycle. This process can effectively reduce the compressor discharge temperature, increase the refrigerant mass flow rate and improve system efficiency.

[0023] The third electronic expansion valve 7 is connected in parallel between the refrigerant outlet of the condenser 2 (the front end of the inlet of the first electronic expansion valve 3) and the refrigerant inlet of the evaporator 6 (the rear end of the outlet of the first electronic expansion valve 3), forming an independent bypass circuit. This circuit is not used for normal refrigeration cycles, but is specifically used for pressure management and safety protection under transient conditions such as system start-up and shutdown and low load.

[0024] The control system receives monitoring signals from sensors located at various key nodes of the system. These sensors include: Te302, condenser outlet water temperature sensor, is used to detect the outlet water temperature of the condenser; Te301, condenser return water temperature sensor, used to detect the return water temperature of the condenser; HX02, condenser, used for the working fluid to release hot water and absorb heat; SF212, condenser safety valve, is used to protect the condenser from pressure exceeding the rated value; HV216, condenser safety valve maintenance manual valve, used for the on / off requirements during condenser safety valve maintenance. FD211, a working fluid filter, is used to filter water from the working fluid and solid impurities from pipelines; HX03, Economizer, is used to improve the compression ratio and enhance heating efficiency and performance; EV205, a branch electronic expansion valve, is used for branch working fluid throttling and evaporation to absorb heat, thereby subcooling another part of the refrigerant; EV201, main circuit electronic expansion valve, adiabatic expansion, throttling and pressure reduction; Te202, evaporator inlet temperature sensor, is used to detect the temperature of the working fluid before it enters the evaporator; Pt202, evaporator inlet pressure sensor, is used to detect the pressure of the working fluid before it enters the evaporator; HV214, working fluid filling nozzle, used for standby extraction and filling of working fluid; HX01-1, Evaporator, used for working fluid to absorb hot water and release heat; Te101, Evaporator Return Water Temperature Sensor, is used to detect the return water temperature of the evaporator; Te102, Evaporator Outlet Water Temperature Sensor, is used to detect the outlet water temperature of the evaporator; HV101, spare manual valve, used for replenishing or draining heat source water; HV102, standby manual valve, used for venting or safety valves at the highest point of the hot water source; HV215, evaporator safety valve maintenance manual valve, used for the on / off needs during evaporator safety valve maintenance; SF211, Evaporator Safety Valve, is used to protect the evaporator from pressure exceeding the rated value; HV211, a shut-off valve, is used for the installation and maintenance of magnetic levitation compressors; Pt203, compressor inlet pressure sensor, is used to detect the pressure of the working fluid before it enters the compressor; Te203, compressor inlet temperature sensor, is used to detect the temperature of the working fluid before it enters the compressor; Pt204, compressor outlet pressure sensor, used to detect the pressure of the working fluid discharged from the compressor; Te204, compressor outlet temperature sensor, is used to detect the temperature of the working fluid discharged from the compressor; CHV201, a shut-off check valve, is used for the installation and maintenance of magnetic levitation compressors to ensure the flow of the working fluid; HV217, manual valve, used to control the on / off of the compressor cooling lines; EV203, electronic expansion valve for compressor cooling, used for compressor cooling; SG211, a sight glass for compressor cooling pipes, is used to observe the state of the working fluid inside the compressor cooling pipes; HV218, manual valve, used to control the on / off of the inverter's cooling pipes; EV204, Electronic Expansion Valve for Inverter Cooling, used for inverter cooling; SG212, Inverter cooling pipe sight glass, used to observe the working fluid condition inside the compressor cooling pipe; VFD, or frequency converter, is used to change the power supply frequency of a compressor to regulate its speed, thereby changing its cooling or heating capacity.

[0025] EV202, bypass electronic expansion valve, used to prevent compressor surge; HV219, manual valve, used to control the on / off state of the gas replenishment and enthalpy enhancement pipe; Te401, a gas injection enthalpy enhancement temperature sensor, is used to detect the temperature of the working fluid in the gas injection enthalpy enhancement pipeline before entering the compressor; Based on the monitoring signals from the aforementioned sensors, the control system is configured to execute the following multi-level control strategy.

[0026] Main control loop: With the condenser outlet water temperature as the final control target, the control system compares the measured value of the condenser outlet water temperature with the set value (e.g., 90℃). The deviation is calculated by the PID control algorithm and outputs a control signal to the magnetic levitation centrifugal compressor 1 to steplessly adjust its operating speed (range: 20,000 - 50,000 rpm), thereby precisely adjusting the heating capacity of the system and achieving stable control of the outlet water temperature.

[0027] From the control loop: Evaporation superheat control: The control system calculates the evaporation superheat based on the saturation temperature corresponding to the evaporator outlet temperature and suction pressure. It dynamically adjusts the opening of the first electronic expansion valve 3 through a PID algorithm to maintain the evaporation superheat within the optimal range of 3-8K. This aims to fully utilize the heat exchange area of ​​the evaporator while ensuring that the liquid carryover rate of the compressor suction is zero, thus preventing liquid slugging.

[0028] Exhaust superheat control: The control system calculates the exhaust superheat based on the saturation temperature corresponding to the compressor exhaust temperature and exhaust pressure. It dynamically adjusts the opening of the second electronic expansion valve 5 through a PID algorithm to control the replenishment flow and status, and maintains the exhaust superheat within a safe range of 10-20K. This aims to optimize system performance and ensure that the exhaust temperature is always within the thermal stability limit of R1234ze (E).

[0029] Safety and start / stop control loop (protection layer): Anti-surge control: The control system calculates the compressor's operating pressure ratio and flow rate in real time. When the system starts up or runs at low load, if it detects that the current operating point is approaching the preset surge boundary of the compressor model, the control system will immediately output a command to open the third electronic expansion valve 7 to a calculated safe opening degree. This operation establishes a bypass flow path, instantly increasing the flow rate through the compressor, allowing it to quickly leave the surge zone and ensuring stable operation.

[0030] Pressure differential balancing and soft start: When the system start-up command is issued, the control system first briefly opens the third electronic expansion valve 7 to its maximum opening, so that the pressure between the condenser (high-pressure side) and the evaporator (low-pressure side) can be quickly balanced. After the system pressure differential is established and stabilized, the magnetic levitation centrifugal compressor 1 is then started. This achieves near-zero pressure differential no-load start-up, greatly reduces the starting current surge, and effectively protects the magnetic bearing system.

[0031] In a preferred embodiment, a magnetic levitation centrifugal compressor with a rated power of 100kW is used. The system is designed to operate at the following conditions: evaporation temperature of 15℃ (heat source is 20℃ wastewater) and condensation temperature of 85℃.

[0032] Under these operating conditions, the control system stably maintains the condenser outlet water temperature within a high-precision range of 90℃ ± 0.5℃. Actual measurements show that the system's coefficient of performance (COP) can reach over 4.5, achieving energy savings of over 75% compared to traditional electric heating methods. Crucially, through economizer circulation and precise exhaust superheat control, the compressor exhaust temperature remains consistently below 90℃, far below the critical temperature of R1234ze(E), ensuring the system's long-term reliability. Furthermore, throughout the entire operation, including start-up and shutdown phases, the system operates smoothly without any surge, verifying the effectiveness of the control strategy.

[0033] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0034] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0035] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to fixed connections or detachable connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

Claims

1. A high-pressure-ratio, high-efficiency magnetically levitated centrifugal high-temperature heat pump system, characterized in that, include: The system comprises a magnetic levitation centrifugal compressor (1), a condenser (2), a first electronic expansion valve (3), an economizer (4), a second electronic expansion valve (5), an evaporator (6), and a control system. The high-temperature heat pump system uses R1234ze (E) as the refrigerant. The magnetic levitation centrifugal compressor (1) is equipped with a main suction port and a gas replenishment enthalpy port. The refrigerant side outlet pipe of the condenser (2) is divided into a main line and a branch line. The main line is connected in sequence to the condensing side of the economizer (4), the first electronic expansion valve (3), and the refrigerant inlet of the evaporator (6). The refrigerant outlet of the evaporator (6) is connected to the main suction port of the magnetic levitation centrifugal compressor (1). The branch line is connected to the inlet of the second electronic expansion valve (5). The outlet of the second electronic expansion valve (5) is connected to the hot side inlet of the economizer (4). The hot side outlet of the economizer (4) is connected to the gas replenishment enthalpy port of the magnetic levitation centrifugal compressor (1). The control system is communicatively connected to the magnetically levitated centrifugal compressor (1), the first electronic expansion valve (3), and the second electronic expansion valve (5), and is configured to perform the following coordinated control operations: The rotational speed of the magnetic levitation centrifugal compressor (1) is adjusted based on the outlet water temperature of the condenser (2); The opening degree of the second electronic expansion valve (5) is adjusted based on the exhaust superheat of the magnetic levitation centrifugal compressor (1); The opening degree of the first electronic expansion valve (3) is adjusted based on the superheat at the outlet of the evaporator (6).

2. The high-pressure-ratio, high-efficiency magnetic levitation centrifugal high-temperature heat pump system according to claim 1, characterized in that: It also includes a third electronic expansion valve (7) connected between the condenser (2) and the evaporator (6).

3. The high-pressure-ratio, high-efficiency magnetic levitation centrifugal high-temperature heat pump system according to claim 1, characterized in that: The third electronic expansion valve (7) is used to prevent surge of the magnetic levitation centrifugal compressor (1) and / or to protect the compressor from liquid slugging during system startup.

4. The high-pressure-ratio, high-efficiency magnetic levitation centrifugal high-temperature heat pump system according to claim 1, characterized in that: The magnetic levitation centrifugal compressor (1) is a single-stage compressor with an operating speed of 20,000-50,000 rpm, achieving a pressure ratio greater than or equal to 6.

5. The high-pressure-ratio, high-efficiency magnetic levitation centrifugal high-temperature heat pump system according to claim 1, characterized in that: The condenser (2) is a shell-and-tube heat exchanger or a plate heat exchanger, and its water channel outlet outputs high-temperature process hot water with a temperature greater than or equal to 90°C.

6. The high-pressure-ratio, high-efficiency magnetic levitation centrifugal high-temperature heat pump system according to claim 1, characterized in that: The water channel of the evaporator (6) is connected to low-temperature wastewater, geothermal tailwater or ambient air source, and the heat source temperature range is 10°C to 40°C.

7. The high-pressure-ratio, high-efficiency magnetic levitation centrifugal high-temperature heat pump system according to claim 1, characterized in that: The control system is also communicatively connected to the third electronic expansion valve (7) and is configured to control the third electronic expansion valve (7) to open to establish a pressure differential and / or prevent surge during system startup or low-load conditions.

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