CN111197786B - High-capacity gradient temperature-increasing type multistage coupling heat pump heat supply system - Google Patents

High-capacity gradient temperature-increasing type multistage coupling heat pump heat supply system Download PDF

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CN111197786B
CN111197786B CN201911335570.5A CN201911335570A CN111197786B CN 111197786 B CN111197786 B CN 111197786B CN 201911335570 A CN201911335570 A CN 201911335570A CN 111197786 B CN111197786 B CN 111197786B
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stage
heat exchanger
flow valve
flow
valve
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CN111197786A (en
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耿鹏鹏
梁波
雷平飞
柴新元
杨吉丰
杨娟香
***
马素霞
赵贯甲
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Shanxi Installation Group Co Ltd
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Shanxi Industrial Equipment Installation Group Co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
    • F24D3/00—Hot-water central heating systems
    • F24D3/18—Hot-water central heating systems using heat pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
    • F24D19/00—Details
    • F24D19/10—Arrangement or mounting of control or safety devices
    • F24D19/1006—Arrangement or mounting of control or safety devices for water heating systems
    • F24D19/1009—Arrangement or mounting of control or safety devices for water heating systems for central heating
    • F24D19/1015—Arrangement or mounting of control or safety devices for water heating systems for central heating using a valve or valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B7/00—Compression machines, plants or systems, with cascade operation, i.e. with two or more circuits, the heat from the condenser of one circuit being absorbed by the evaporator of the next circuit
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
    • F24D2200/00—Heat sources or energy sources
    • F24D2200/12—Heat pump
    • F24D2200/123—Compression type heat pumps

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Heat-Pump Type And Storage Water Heaters (AREA)

Abstract

The invention relates to a high-capacity gradient temperature-increasing multistage coupling heat pump heating system, and belongs to the field of vapor compression heat pump systems in distributed energy supply systems. The flow of circulating water of each stage is controlled by designing a triple-overlapping heat pump heating system and then utilizing a first-stage circulating pump and a third-stage circulating pump to be matched with a third-stage third flow valve and a first-stage flow control valve, so that the water temperature of the inlet and the outlet of each stage of heat pump reaches a preset value or a given value. Through the high-capacity gradient temperature-increasing multistage coupling heat pump heat supply system, the primary network heat supply hot water is heated in a gradient manner, so that the average heat absorption temperature difference of the primary network water is reduced, the heat supply efficiency of a thermal power plant is improved, and the thermoelectric coupling contradiction is relieved.

Description

High-capacity gradient temperature-increasing type multistage coupling heat pump heat supply system
Technical Field
The invention relates to a high-capacity gradient temperature-increasing multistage coupling heat pump heating system, and belongs to the field of vapor compression heat pump systems in distributed energy supply systems.
Background
With the continuous promotion of the urbanization process of China, particularly in northern cities of China, the heating load in winter is larger and larger, the requirement on the heating load is further improved, and the capacity limit of a city heating system is limited. In order to meet the continuously rising heating demand and the heat supply load demand of a newly-born house, the capacity expansion of an old heat supply system is needed, but the urban heat supply system is complex, the modification work amount is large, the construction period is long, and the rapidly-increasing energy supply demand is difficult to meet. In addition, a large number of supplementary heating modes such as a regional boiler room and the like generally have the problems of low energy utilization rate, pollution discharge amplification and the like. One of the common heat supply modes at present is to utilize extraction steam of a thermal power plant to heat a primary network to return water for heat supply, although the heat and power cogeneration mode realizes the cascade utilization of energy, the heat efficiency of the system can reach 80%, the method directly uses high-grade heat with higher temperature and pressure for heating network water, still has irreversible loss, and the internal efficiency of a steam turbine can be reduced to a certain extent due to the influence of extraction steam. Another significant problem of air extraction and heat supply is that the thermoelectric coupling effect is significant, and is not beneficial to peak regulation control of the power grid. In recent years, the contradiction is aggravated by the rapid rise of new energy sources such as solar energy, wind energy and the like. Because the power grid firstly needs to absorb the electric energy generated by the new energy, the peak regulation task of the thermal power plant is harder, and the contradiction has a trend of being more and more excited in the heating period in winter in the north.
For a thermal power plant with a plurality of units, the exhaust backpressure of the thermal power plant is gradually increased by reforming a steam turbine, and the exhaust condensation waste heat at different temperatures is utilized to heat the primary network backwater in a gradient manner, so that the heat supply temperature can be effectively reduced, and the irreversible loss of temperature difference is reduced. The technology is adopted for long-distance heat supply from the ancient city to the Taiyuan city in China, and compared with the steam extraction heating of the traditional thermal power plant, the technology has the obvious energy-saving effect. However, this solution has two main problems: firstly, the method is only suitable for a thermal power plant with a plurality of units, and the plurality of units must operate simultaneously during heat supply; secondly, the thermal coupling condition can be more serious after the high back pressure of the steam turbine is improved. In addition, the absorption heat pump technology is also used for heating, but in the peak period of heating in winter, the economical efficiency of operation is not better than that of directly adopting air extraction for heating, and the operation and maintenance cost of the lithium bromide heat pump system is high, thus preventing the application of the technology in heating. The single-stage compression heat pump can also utilize the exhaust waste heat of the steam turbine to heat the primary network backwater, but because the temperature difference is large, the heat supply coefficient is often low, the pressure ratio is large, a large-capacity centrifugal compressor cannot be adopted, and the heat supply capacity is limited.
Disclosure of Invention
The embodiment of the invention provides a novel high-capacity gradient temperature-increasing type multistage coupling heat pump heat supply system, and solves the technical problems that in the prior art, the heat supply efficiency is low, and a high pressure ratio of a single heat pump cannot utilize a high-capacity centrifugal compressor.
In order to achieve the above object, an embodiment of the present invention provides a large-capacity gradient temperature-increasing multistage coupling heat pump heating system, which includes a first-stage evaporation heat exchanger, a first-stage compressor, a first-stage circulation pump, a first-stage flow control valve, a first-stage front condensation heat exchanger, a first-stage rear condensation heat exchanger, a first-stage expansion valve, a second-stage first flow valve, a second-stage front condensation heat exchanger, a second-stage expansion valve, a second-stage condensation heat exchanger, a second-stage compressor, a second-stage second flow valve, a second-stage third flow valve, a second-stage rear condensation heat exchanger, a third-stage first flow valve, a third-stage second flow valve, a third-stage condensation heat exchanger, a third-stage expansion valve, a third-stage evaporation heat exchanger, a third-stage compressor, a third-stage circulation pump, a third-stage third flow valve, an air;
a circulating water inlet pipe and a circulating water outlet pipe are respectively connected with a water inlet and a water outlet of the first-stage evaporation heat exchanger; one end of the first-stage compressor is connected with a heat exchange water outlet of the first-stage evaporation heat exchanger, and the other end of the first-stage compressor is connected with a heat exchange water inlet of the first-stage front condensation heat exchanger; the heat exchange water outlet of the first-stage front condensation heat exchanger is connected with the heat exchange water inlet of the first-stage rear condensation heat exchanger; the heat exchange water outlet of the first-stage post-condensation heat exchanger is connected with the inlet end of a first-stage expansion valve, and the outlet end of the first-stage expansion valve is connected with the heat exchange water inlet of the first-stage evaporation heat exchanger; the circulating water inlet pipe is sequentially connected with the water inlet of the first-stage front condensation heat exchanger through a first-stage circulating pump and a first-stage flow control valve, and the water outlet of the first-stage front condensation heat exchanger is simultaneously connected with one end of a second-stage first flow valve, the water inlet of the second-stage condensation heat exchanger and the water outlet of a third-stage evaporation heat exchanger through a second-stage fourth flow control valve; the primary net water inlet is communicated with the water inlet of the first-stage post-condensation heat exchanger, and the water outlet of the first-stage post-condensation heat exchanger is communicated with the water inlet of the second-stage post-condensation heat exchanger; the other end of the second-stage first flow valve is connected with a water inlet of the second-stage front condensation heat exchanger; the water outlet of the second-stage front condensation heat exchanger is communicated with the water inlet of the third-stage evaporation heat exchanger through a third-stage circulating pump and a third-stage third flow valve; the water outlet of the second-stage condensation heat exchanger is connected with a circulating water outlet pipe; the water outlet of the second-stage post-condensation heat exchanger is communicated with the water inlet of the third-stage condensation heat exchanger through a third-stage second flow valve, and is connected with the water inlet of the air extraction heater through a third-stage first flow valve; the heat exchange water inlet of the second-stage front condensation heat exchanger is connected with the heat exchange water outlet of the second-stage condensation heat exchanger through a second-stage second flow valve and a second-stage compressor; one end of the second-stage third flow valve is communicated with the water outlet of the second-stage compressor, and the other end of the second-stage third flow valve is connected with the heat exchange water outlet of the second-stage front condensation heat exchanger and the heat exchange water inlet of the second-stage rear condensation heat exchanger; the heat exchange water outlet of the second-stage post-condensation heat exchanger is connected with the heat exchange water inlet of the second-stage condensation heat exchanger through a second-stage expansion valve; the water outlet of the third-stage condensation heat exchanger is connected with the water inlet of the air extraction heater, and the water outlet of the air extraction heater is used as a primary net water outlet; and a heat exchange water inlet of the third-stage condensation heat exchanger is connected with a heat exchange water outlet of the third-stage evaporation heat exchanger through a third-stage compressor, and a heat exchange water outlet of the third-stage condensation heat exchanger is communicated with a heat exchange hot water port of the third-stage evaporation heat exchanger through a third-stage expansion valve.
Furthermore, the first-stage evaporation heat exchanger absorbs the heat of a part of circulating water, and the first-stage front condensation heat exchanger of the first-stage heat pump system heats a first part of circulating water; the temperature of the primary net water is heated to t2 from t1 by a first-stage post-condensation heat exchanger of the first-stage heat pump system; the circulating water of the third-stage heat pump system is mixed with the first part of circulating water to be used as a heat source of the second-stage heat pump system; the second-stage fourth flow regulating valve is used for regulating the flow of circulating water entering a second-stage condensing heat exchanger of the second-stage heat pump system; circulating water of the second-stage heat pump is heated by the second-stage front condensing heat exchanger and enters a third-stage evaporating heat exchanger of a third-stage heat pump system through a third-stage circulating pump and a third-stage third flow valve; the second-stage second flow valve and the second-stage third flow valve are used for controlling the temperature of the circulating water inlet of the third-stage evaporative heat exchanger; the second-stage first flow valve, the third-stage third flow valve and the second-stage fourth flow regulating valve jointly regulate the flow entering the third-stage evaporation heat exchanger; the primary net water is heated to t3 through a second-stage post-condensation heat exchanger of the second-stage heat pump heating system; the third stage heat pump system further increases the temperature of the primary wire water to t4 through a third stage condensing heat exchanger.
Further, the third stage first flow valve and the third stage second flow valve are used for adjusting the temperature of t4, and the temperature of the primary net water is further increased to the heating temperature from t4 through the suction heater.
Furthermore, when the return water temperature of the primary network is less than or equal to a preset value, the high-capacity gradient temperature-increasing multistage coupling heat pump heating system heats the primary network through a three-stage heat pump system to realize that the water temperature at the inlet and the outlet of each stage of heat pump reaches a given value; heating by using a three-stage heat pump, and controlling the flow of circulating water of each stage by using two circulating pumps matched with a third-stage third flow valve and a first-stage flow control valve so as to realize that the water temperature of an inlet and an outlet of each stage of heat pump reaches a given value; when the three-stage heat pump system is used for heating, the third-stage second flow valve, the second-stage first flow valve, the second-stage fourth flow regulating valve and the second-stage second flow valve are opened, and the third-stage first flow valve and the second-stage third flow valve are closed.
And further, when the return water temperature of the primary network is greater than a preset value, heating is carried out through a two-stage heat pump system.
Compared with the prior art, the invention has the beneficial effects that: 1. the multi-stage heat pump is coupled with the gradient heating heat supply, so that the average heat supply temperature is reduced, and the heat supply efficiency is improved; 2. the pressure ratio of the single-stage heat pump is reduced, and a large-capacity centrifugal compressor is favorably adopted; 3. the method can be applied to a large-capacity heat pump heating system; 4. the low-temperature waste heat of the steam or the flue gas is more conveniently utilized.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings required in the description of the embodiments are briefly introduced below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, without any inventive work, other drawings can be obtained from the drawings, and the technical solution directly obtained from the drawings shall also belong to the protection scope of the present invention.
FIG. 1 is a block diagram of an embodiment of the present invention.
Description of reference numerals: : 1. a first stage evaporative heat exchanger; 2. a first stage compressor; 3. a first stage circulating pump; 4. a first stage flow control valve; 5. a first stage front condensing heat exchanger; 6. a first stage post-condensing heat exchanger; 7. a first stage expansion valve; 8. a second stage first flow valve; 9. a second stage front condensing heat exchanger; 10. a second stage expansion valve; 11. a second stage condensing heat exchanger; 12. a second stage compressor; 13. a second stage second flow valve; 14. a second stage third flow valve; 15. a second stage post-condensing heat exchanger; 16. a third stage first flow valve; 17. a third stage second flow valve; 18. a third stage condensing heat exchanger; 19. a third stage expansion valve; 20. a third stage evaporative heat exchanger; 21. a third stage compressor; 22. a third stage circulation pump; 23. a third stage third flow valve; 24. an air extraction heater; 25. and the second-stage fourth flow regulating valve.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terms "first" and "second," and the like, in the description and in the claims of embodiments of the present invention are used for distinguishing between different objects and not for describing a particular order of the objects. For example, the first parameter set and the second parameter set, etc. are used to distinguish different parameter sets, rather than to describe a particular order of parameter sets.
In the description of the embodiments of the present invention, the meaning of "a plurality" means two or more unless otherwise specified. For example, a plurality of elements refers to two elements or more.
The term "and/or" herein is an association relationship describing an associated object, and means that there may be three relationships, for example, a display panel and/or a backlight, which may mean: there are three cases of a display panel alone, a display panel and a backlight at the same time, and a backlight alone. The symbol "/" herein denotes a relationship in which the associated object is or, for example, input/output denotes input or output.
In the embodiments of the present invention, words such as "exemplary" or "for example" are used to mean serving as examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "e.g.," an embodiment of the present invention is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word "exemplary" or "such as" is intended to present concepts related in a concrete fashion.
The embodiment of the invention provides a high-capacity gradient temperature-increasing type multistage coupling heat pump heating system, which specifically comprises a first-stage evaporation heat exchanger 1, a first-stage compressor 2, a first-stage circulating pump 3, a first-stage flow control valve 4, a first-stage front condensation heat exchanger 5, a first-stage rear condensation heat exchanger 6, a first-stage expansion valve 7, a second-stage first flow valve 8, a second-stage front condensation heat exchanger 9, a second-stage expansion valve 10, a second-stage condensation heat exchanger 11, a second-stage compressor 12, a second-stage second flow valve 13, a second-stage third flow valve 14, a second-stage rear condensation heat exchanger 15, a third-stage first flow valve 16, a third-stage second flow valve 17, a third-stage condensation heat exchanger 18, a third-stage expansion valve 19, a third-stage evaporation heat exchanger 20, a third-stage compressor 21, a third-stage circulating pump 22, a third-stage third flow valve 23, A bleed air heater 24 and a second-stage fourth flow regulating valve 25;
a circulating water inlet pipe and a circulating water outlet pipe are respectively connected with a water inlet and a water outlet of the first-stage evaporation heat exchanger 1; one end of the first-stage compressor 2 is connected with a heat exchange water outlet of the first-stage evaporation heat exchanger 1, and the other end of the first-stage compressor is connected with a heat exchange water inlet of the first-stage front condensation heat exchanger 5; the heat exchange water outlet of the first-stage front condensation heat exchanger 5 is connected with the heat exchange water inlet of the first-stage rear condensation heat exchanger 6; a heat exchange water outlet of the first-stage post-condensation heat exchanger 6 is connected with an inlet end of a first-stage expansion valve 7, and an outlet end of the first-stage expansion valve 7 is connected with a heat exchange water inlet of the first-stage evaporation heat exchanger 1; a circulating water inlet pipe is sequentially connected with a water inlet of a first-stage front condensation heat exchanger 5 through a first-stage circulating pump 3 and a first-stage flow control valve 4, and a water outlet of the first-stage front condensation heat exchanger 5 is simultaneously connected with one end of a second-stage first flow valve 8, a water inlet of a second-stage condensation heat exchanger 11 and a water outlet of a third-stage evaporation heat exchanger 20 through a second-stage fourth flow control valve 25; a primary net water inlet is communicated with a water inlet of the first-stage post-condensation heat exchanger 6, and a water outlet of the first-stage post-condensation heat exchanger 6 is communicated with a water inlet of the second-stage post-condensation heat exchanger 15; the other end of the second-stage first flow valve 8 is connected with a water inlet of a second-stage front condensation heat exchanger 9; the water outlet of the second-stage front condensation heat exchanger 9 is communicated with the water inlet of the third-stage evaporation heat exchanger 20 through a third-stage circulating pump 22 and a third-stage third flow valve 23; the water outlet of the second-stage condensation heat exchanger 11 is connected with a circulating water outlet pipe; the water outlet of the second-stage post-condensation heat exchanger 15 is communicated with the water inlet of the third-stage condensation heat exchanger 18 through a third-stage second flow valve 17, and is connected with the water inlet of the suction heater 24 through a third-stage first flow valve 16; a heat exchange water inlet of the second-stage front condensation heat exchanger 9 is connected with a heat exchange water outlet of the second-stage condensation heat exchanger through a second-stage second flow valve 13 and a second-stage compressor 12; one end of the second-stage third flow valve 14 is communicated with the water outlet of the second-stage compressor, and the other end of the second-stage third flow valve is connected with the heat exchange water outlet of the second-stage front condensation heat exchanger 9 and the heat exchange water inlet of the second-stage rear condensation heat exchanger 15; a heat exchange water outlet of the second-stage post-condensation heat exchanger 15 is connected with a heat exchange water inlet of the second-stage condensation heat exchanger through a second-stage expansion valve 10; the water outlet of the third-stage condensation heat exchanger 18 is connected with the water inlet of the air extraction heater 24, and the water outlet of the air extraction heater 24 is used as a primary net water outlet; a heat exchange water inlet of the third-stage condensation heat exchanger 18 is connected with a heat exchange water outlet of the third-stage evaporation heat exchanger 20 through a third-stage compressor 21, and a heat exchange water outlet of the third-stage condensation heat exchanger 18 is communicated with a heat exchange hot water port of the third-stage evaporation heat exchanger 20 through a third-stage expansion valve 19.
The high-capacity gradient temperature-increasing type multistage coupling heat pump heat supply system provided by the embodiment controls the flow of circulating water of each stage by designing a triple-overlapping type heat pump heat supply system and then by utilizing the first-stage circulating pump 3 and the third-stage circulating pump 22 and matching the third-stage third flow valve 23 and the first-stage flow control valve 4, so that the water temperature of the inlet and the outlet of each stage of heat pump reaches a preset value or a given value. Through the high-capacity gradient temperature-increasing multistage coupling heat pump heat supply system, the primary network heat supply hot water is heated in a gradient manner, so that the average heat absorption temperature difference of the primary network water is reduced, the heat supply efficiency of a thermal power plant is improved, and the thermoelectric coupling contradiction is relieved.
In the embodiment of the invention, a first-stage evaporation heat exchanger 1 absorbs the heat of a part of circulating water, and a first-stage front condensation heat exchanger 5 of a first-stage heat pump system (comprising the first-stage evaporation heat exchanger 1, a first-stage compressor 2, a first-stage front condensation heat exchanger 5, a first-stage rear condensation heat exchanger 6 and a first-stage expansion valve 7) is used for heating the first part of circulating water; the first-stage post-condensation heat exchanger 6 of the first-stage heat pump system heats the temperature of the primary net water from t1 to t 2; the circulating water of the third-stage heat pump system is mixed with the first part of circulating water and then is used as a heat source of a second-stage heat pump system (comprising a second-stage front condensation heat exchanger 9, a second-stage expansion valve 10, a second-stage condensation heat exchanger 11, a second-stage compressor 12 and a second-stage rear condensation heat exchanger 15); the second-stage fourth flow regulating valve 25 is used for regulating the flow of circulating water entering the second-stage condensation heat exchanger 11 of the second-stage heat pump system; the second-stage heat pump circulating water is heated by a second-stage front condensing heat exchanger 9 and enters a third-stage evaporating heat exchanger 20 of a third-stage heat pump system through a third-stage circulating pump 22 and a third-stage third flow valve 23; the second-stage second flow valve 13 and the second-stage third flow valve 14 are used for controlling the temperature of the circulating water inlet of the third-stage evaporative heat exchanger 20; the second-stage first flow valve 8, the third-stage third flow valve 23 and the second-stage fourth flow regulating valve 25 jointly regulate the flow entering the third-stage evaporative heat exchanger 20; the primary net water is heated to t3 through a second stage post-condensing heat exchanger 15 of the second stage heat pump heating system; the third stage heat pump system further increases the temperature of the primary wire water to t4 through the third stage condensing heat exchanger 18.
The first-stage evaporation heat exchanger 1 absorbs the heat of a part of circulating water, and heats the first part of circulating water through a first-stage front condensation heat exchanger 5 of a first-stage heat pump system; the first-stage post-condensation heat exchanger 6 of the first-stage heat pump system heats the temperature of the primary net water from t1 to t 2; the circulating water of the third-stage heat pump system is mixed with the first part of circulating water to be used as a heat source of the second-stage heat pump system; the second-stage fourth flow regulating valve 25 is used for regulating the flow of circulating water entering the second-stage condensation heat exchanger 11 of the second-stage heat pump system; the second-stage heat pump circulating water is heated by a second-stage front condensing heat exchanger 9 and enters a third-stage evaporating heat exchanger 20 of a third-stage heat pump system through a third-stage circulating pump 22 and a third-stage third flow valve 23; the second-stage second flow valve 13 and the second-stage third flow valve 14 are used for controlling the temperature of the circulating water inlet of the third-stage evaporative heat exchanger 20; the second-stage first flow valve 8, the third-stage third flow valve 23 and the second-stage fourth flow regulating valve 25 jointly regulate the flow entering the third-stage evaporative heat exchanger 20; the primary net water is heated to t3 through a second stage post-condensing heat exchanger 15 of the second stage heat pump heating system; the third stage heat pump system further increases the temperature of the primary wire water to t4 through the third stage condensing heat exchanger 18.
Illustratively, the third stage first flow valve 16 and the third stage second flow valve 17 are used to adjust the temperature t4, further increasing the temperature of the primary net water from t4 to the heating temperature by the suction heater 24.
In the large-capacity gradient temperature-increasing type multistage coupling heat pump heating system, when the return water temperature of a primary network is less than or equal to a preset value, the water temperature of an inlet and an outlet of each stage of heat pump reaches a given value through heating of a three-stage heat pump system; heating by using three stages of heat pumps, and controlling the flow of circulating water of each stage by using two circulating pumps in the system to cooperate with a third flow valve and a first flow control valve so as to realize that the water temperature of an inlet and an outlet of each stage of heat pump reaches a given value; when the three-stage heat pump system is adopted for heating, the third-stage second flow valve 17, the second-stage first flow valve 8, the second-stage fourth flow regulating valve 25 and the second-stage second flow valve 13 are opened, and the third-stage first flow valve 16 and the second-stage third flow valve 14 are closed; and when the return water temperature of the primary network is greater than a preset value, heating by a two-stage heat pump system.
By the multistage heat pump coupling gradient temperature-increasing heat supply described in the embodiment, the average heat supply temperature is reduced, and the heat supply efficiency is improved; the pressure ratio of the single-stage heat pump is reduced, and a large-capacity centrifugal compressor is favorably adopted; the method can be applied to a large-capacity heat pump heating system; the low-temperature waste heat of the steam or the flue gas is more conveniently utilized.
Table 1 below is a selection of flow rates versus temperature as described in the examples of the invention.
Figure GDA0002835387110000111
The following table 2 shows the preliminary values of the temperatures of the respective points.
Figure GDA0002835387110000121
Exemplary, as shown in tables 1 and 2:
wherein t is1-t4Representing the water temperature, t, of the primary net water in different stagesx1-tx8Representing the water temperature, q, of the circulating water at different stages1-q3Represents the circulating water flow rate, and q represents the primary network water flow rate.
The system is designed on the basis of an absorption heat exchanger unit, so that the return water of a primary network is 25 ℃. The highest temperature that the compression heat pump can heat to is influenced by the compressor, in order to guarantee the high-efficient and safe operation of compressor, get the net export temperature of water 90 ℃. To ensure that the turbine is efficient and stable, tx7Should be made as low as possible, but tx7Too low will result in too low a first stage heat pump evaporating pressure, too high a pressure ratio, reduced COP, two phase trade-off tx7The temperature was taken at 20 ℃. In the same way, tx6Taken at 30 ℃. Due to q1>q2+q3Temperature t after mixing of the twox8Below 25 ℃. To facilitate flow control and model calculation, take tx2＝tx4＝tx5。
In order to ensure that the pressure ratio and the COP of each stage do not differ too much, the temperature rise of circulating water of each stage is close to the total temperature rise of 1/3, and the temperature difference of a high-temperature heat source and a low-temperature heat source of a first-stage heat pump is properly reduced in order to ensure that the COP of a system is larger due to the maximum heat exchange amount of the first-stage heat pump.
The heat pump is changed to a two-stage heat pump under the variable working condition.
Under normal working conditions, three stages of heat pumps are used for heating, and the first-stage circulating pump 3 and the third-stage circulating pump 22 in the figure 1 are matched with the valves, the third-stage flow valve 23 and the first-stage flow control valve 4 to control the flow of circulating water of each stage, so that the water temperature of the inlet and the outlet of each stage of heat pump reaches a given value. When the heat load of a user is smaller than the heat supply load and the return water temperature of a primary network is too high, the situation that one-stage heat pumps are reduced can be considered, and two-stage heat pumps are adopted for heating. When the three-stage heat pump is adopted, the third-stage second flow valve 17, the second-stage first flow valve 8, the second-stage fourth flow regulating valve 25 and the second-stage second flow valve 13 are opened, and the third-stage first flow valve 16 and the second-stage third flow valve 14 are closed. When the two-stage heat pump is adopted, the valve switching condition is opposite to that of the three-stage heat pump, namely, the third-stage second flow valve 17, the second-stage first flow valve 8, the second-stage fourth flow regulating valve 25 and the second-stage second flow valve 13 are opened, the third-stage first flow valve 16 and the second-stage third flow valve 14 are closed, and the third-stage first flow valve 16 and the second-stage third flow valve 14 are opened. The two-stage heat pump is not used under normal working conditions because the two-stage heat pump leads to the increase of the pressure ratio of each stage of compressor, the efficiency and the safe operation are influenced, and after the stage number is reduced to two stages, the temperature difference of a high-low temperature heat source is increased, the COP is reduced, the required suction capacity of each stage of compression stage is also increased, and the manufacturing, installation and examination of the compressor are increased. However, if the number of stages is too many, the cost is greatly improved, the difficulty degree of matching the temperature and the flow between each stage is doubled, and the occupied area of the system is increased. Comprehensively, the three-stage heat pump is suitable.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (5)

1. A high-capacity gradient temperature-increasing type multistage coupling heat pump heating system is characterized in that: the system comprises a first-stage evaporation heat exchanger, a first-stage compressor, a first-stage circulating pump, a first-stage flow control valve, a first-stage front condensation heat exchanger, a first-stage rear condensation heat exchanger, a first-stage expansion valve, a second-stage first flow valve, a second-stage front condensation heat exchanger, a second-stage expansion valve, a second-stage condensation heat exchanger, a second-stage compressor, a second-stage second flow valve, a second-stage third flow valve, a second-stage rear condensation heat exchanger, a third-stage first flow valve, a third-stage second flow valve, a third-stage condensation heat exchanger, a third-stage expansion valve, a third-stage evaporation heat exchanger, a third-stage compressor, a third-stage circulating pump, a third-stage third flow valve, an air extraction heater and;
a circulating water inlet pipe and a circulating water outlet pipe are respectively connected with a water inlet and a water outlet of the first-stage evaporation heat exchanger; one end of the first-stage compressor is connected with a heat exchange water outlet of the first-stage evaporation heat exchanger, and the other end of the first-stage compressor is connected with a heat exchange water inlet of the first-stage front condensation heat exchanger; the heat exchange water outlet of the first-stage front condensation heat exchanger is connected with the heat exchange water inlet of the first-stage rear condensation heat exchanger; the heat exchange water outlet of the first-stage post-condensation heat exchanger is connected with the inlet end of a first-stage expansion valve, and the outlet end of the first-stage expansion valve is connected with the heat exchange water inlet of the first-stage evaporation heat exchanger; the circulating water inlet pipe is sequentially connected with the water inlet of the first-stage front condensation heat exchanger through a first-stage circulating pump and a first-stage flow control valve, and the water outlet of the first-stage front condensation heat exchanger is simultaneously connected with one end of a second-stage first flow valve, the water inlet of the second-stage condensation heat exchanger and the water outlet of a third-stage evaporation heat exchanger through a second-stage fourth flow control valve; the primary net water inlet is communicated with the water inlet of the first-stage post-condensation heat exchanger, and the water outlet of the first-stage post-condensation heat exchanger is communicated with the water inlet of the second-stage post-condensation heat exchanger; the other end of the second-stage first flow valve is connected with a water inlet of the second-stage front condensation heat exchanger; the water outlet of the second-stage front condensation heat exchanger is communicated with the water inlet of the third-stage evaporation heat exchanger through a third-stage circulating pump and a third-stage third flow valve; the water outlet of the second-stage condensation heat exchanger is connected with a circulating water outlet pipe; the water outlet of the second-stage post-condensation heat exchanger is communicated with the water inlet of the third-stage condensation heat exchanger through a third-stage second flow valve, and is connected with the water inlet of the air extraction heater through a third-stage first flow valve; the heat exchange water inlet of the second-stage front condensation heat exchanger is connected with the heat exchange water outlet of the second-stage condensation heat exchanger through a second-stage second flow valve and a second-stage compressor; one end of the second-stage third flow valve is communicated with the water outlet of the second-stage compressor, and the other end of the second-stage third flow valve is connected with the heat exchange water outlet of the second-stage front condensation heat exchanger and the heat exchange water inlet of the second-stage rear condensation heat exchanger; the heat exchange water outlet of the second-stage post-condensation heat exchanger is connected with the heat exchange water inlet of the second-stage condensation heat exchanger through a second-stage expansion valve; the water outlet of the third-stage condensation heat exchanger is connected with the water inlet of the air extraction heater, and the water outlet of the air extraction heater is used as a primary net water outlet; and a heat exchange water inlet of the third-stage condensation heat exchanger is connected with a heat exchange water outlet of the third-stage evaporation heat exchanger through a third-stage compressor, and a heat exchange water outlet of the third-stage condensation heat exchanger is communicated with a heat exchange hot water port of the third-stage evaporation heat exchanger through a third-stage expansion valve.
2. The high-capacity gradient temperature-increasing type multistage-coupled heat pump heating system according to claim 1, characterized in that: the first-stage evaporation heat exchanger absorbs the heat of a part of circulating water, and the first-stage front condensation heat exchanger of the first-stage heat pump system heats the first part of circulating water; the temperature of the primary net water is heated to t2 from t1 by a first-stage post-condensation heat exchanger of the first-stage heat pump system; the circulating water of the third-stage heat pump system is mixed with the first part of circulating water to be used as a heat source of the second-stage heat pump system; the second-stage fourth flow regulating valve is used for regulating the flow of circulating water entering a second-stage condensing heat exchanger of the second-stage heat pump system; circulating water of the second-stage heat pump is heated by the second-stage front condensing heat exchanger and enters a third-stage evaporating heat exchanger of a third-stage heat pump system through a third-stage circulating pump and a third-stage third flow valve; the second-stage second flow valve and the second-stage third flow valve are used for controlling the temperature of the circulating water inlet of the third-stage evaporative heat exchanger; the second-stage first flow valve, the third-stage third flow valve and the second-stage fourth flow regulating valve jointly regulate the flow entering the third-stage evaporation heat exchanger; the primary net water is heated to t3 through a second-stage post-condensation heat exchanger of the second-stage heat pump heating system; the third stage heat pump system further increases the temperature of the primary wire water to t4 through a third stage condensing heat exchanger.
3. The high-capacity gradient temperature-increasing type multistage-coupled heat pump heating system according to claim 2, characterized in that: and the third-stage first flow valve and the third-stage second flow valve are used for adjusting the temperature of t4, and the temperature of the primary net water is further increased to the heating temperature from t4 through the suction heater.
4. The high-capacity gradient temperature-increasing type multistage-coupled heat pump heating system according to claim 3, characterized in that: when the return water temperature of the primary network is less than or equal to a preset value, the high-capacity gradient temperature-increasing type multistage coupling heat pump heat supply system heats the primary network through the three-stage heat pump system to realize that the water temperature of the inlet and the outlet of each stage of heat pump reaches a given value; heating by using a three-stage heat pump, and controlling the flow of circulating water of each stage by using two circulating pumps matched with a third-stage third flow valve and a first-stage flow control valve so as to realize that the water temperature of an inlet and an outlet of each stage of heat pump reaches a given value; when the three-stage heat pump system is used for heating, the third-stage second flow valve, the second-stage first flow valve, the second-stage fourth flow regulating valve and the second-stage second flow valve are opened, and the third-stage first flow valve and the second-stage third flow valve are closed.
5. The high-capacity gradient temperature-increasing type multistage-coupled heat pump heating system according to claim 4, characterized in that: and when the return water temperature of the primary network is greater than a preset value, heating by a two-stage heat pump system.
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