CN114941914A - Control method of cascade heat pump system - Google Patents
Control method of cascade heat pump system Download PDFInfo
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- CN114941914A CN114941914A CN202210471162.8A CN202210471162A CN114941914A CN 114941914 A CN114941914 A CN 114941914A CN 202210471162 A CN202210471162 A CN 202210471162A CN 114941914 A CN114941914 A CN 114941914A
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- 238000000034 method Methods 0.000 title claims abstract description 40
- 239000003507 refrigerant Substances 0.000 claims abstract description 87
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims abstract description 80
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 80
- 239000011737 fluorine Substances 0.000 claims abstract description 80
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 239000007788 liquid Substances 0.000 description 6
- 238000000926 separation method Methods 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- LVGUZGTVOIAKKC-UHFFFAOYSA-N 1,1,1,2-tetrafluoroethane Chemical compound FCC(F)(F)F LVGUZGTVOIAKKC-UHFFFAOYSA-N 0.000 description 1
- 238000003889 chemical engineering Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000013507 mapping Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 239000004753 textile Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- 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
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H4/00—Fluid heaters characterised by the use of heat pumps
- F24H4/02—Water heaters
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- 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
- F25B41/00—Fluid-circulation arrangements
- F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
- F25B41/24—Arrangement of shut-off valves for disconnecting a part of the refrigerant cycle, e.g. an outdoor part
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- 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
- F25B41/00—Fluid-circulation arrangements
- F25B41/40—Fluid line arrangements
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- 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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
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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)
- Air Conditioning Control Device (AREA)
Abstract
The invention relates to the technical field of cascade heat pumps, in particular provides a control method of a cascade heat pump system, and aims to solve the problem that the existing cascade heat pump system is low in operation energy efficiency. For the purpose, the cascade heat pump system comprises a high-pressure refrigerant circulation loop and a low-pressure refrigerant circulation loop, wherein the high-pressure refrigerant circulation loop and the low-pressure refrigerant circulation loop can exchange heat through an intermediate heat exchanger; the cascade heat pump system can acquire the actual demand load of the system and control the second compressor and the fluorine pump to operate alternatively according to the actual demand load of the system. Based on the control mode, the cascade heat pump system can selectively control the second compressor and the fluorine pump to be alternatively connected into the low-pressure refrigerant circulation loop according to actual conditions, so that the second compressor is effectively prevented from being always in an operating state, the energy utilization rate of the system can be improved, and the operating energy efficiency of the system can be improved.
Description
Technical Field
The invention relates to the technical field of cascade heat pumps, and particularly provides a control method of a cascade heat pump system.
Background
With the popularization of policies of energy conservation and emission reduction, industries such as food processing, textile, chemical engineering and the like use high-temperature heat pump systems to carry out high-temperature heating treatment in more and more application occasions. With the increasing demand of industrial heating, the application requirements of users on high-temperature heat pump systems are higher and higher. Firstly, the final heat supply temperature of a high-temperature heat pump system generally needs to be more than 70 ℃, and some heat pump systems even need to exceed 90 ℃; secondly, the environmental conditions to which the high temperature heat pump system is applied also span a very large amount, the outdoor ambient temperature ranges from-30 ℃ to 35 ℃, and high temperature hot water or hot air needs to be supplied in both winter and summer.
In particular, the high temperature hot water used in industry is high, which results in that the common heat pump system is often difficult to reach the actual heating use requirement, and the technology of the cascade heat pump system for providing high temperature hot water is mature. The cascade heat pump system generally comprises a high-pressure refrigerant circulation loop and a low-pressure refrigerant circulation loop, wherein the high-pressure refrigerant circulation loop and the low-pressure refrigerant circulation loop exchange heat through a shared intermediate heat exchanger to achieve the purpose of providing high-temperature hot water. However, the existing cascade heat pump system still needs to operate in a cascade mode outside a rated working condition, for example, when the outdoor environment temperature is relatively high, that is, two-stage compression is still adopted under the working condition that the temperature difference between the evaporation temperature and the condensation temperature is relatively small, and the adjustment flexibility of the setting mode is not high, so that the loss is relatively large, the operation energy efficiency of the cascade heat pump system is low, and the energy waste is caused.
Accordingly, there is a need in the art for a new control method for a cascade heat pump system to solve the above technical problems.
Disclosure of Invention
The present invention is directed to solving the above-mentioned problems, i.e., solving the problem of low energy efficiency of the existing cascade heat pump system.
The invention provides a control method of a cascade heat pump system, wherein the cascade heat pump system comprises a high-pressure refrigerant circulation loop and a low-pressure refrigerant circulation loop, a first compressor, a first heat exchanger, a first throttling component and an intermediate heat exchanger are arranged on the high-pressure refrigerant circulation loop, a second compressor, the intermediate heat exchanger, a fluorine pump, a second throttling component and a second heat exchanger are arranged on the low-pressure refrigerant circulation loop, the high-pressure refrigerant circulation loop and the low-pressure refrigerant circulation loop are arranged to exchange heat through the intermediate heat exchanger, and the second compressor and the fluorine pump are arranged to be capable of alternatively operating;
under the condition that the high-pressure refrigerant circulating loop operates, the control method comprises the following steps:
acquiring the actual demand load of the system;
and controlling the second compressor and the fluorine pump to alternatively operate according to the actual demand load of the system.
In a preferred embodiment of the above control method, the step of "controlling the second compressor and the fluorine pump to alternatively operate according to the actual demand load of the system" specifically includes:
if the actual demand load of the system is greater than a first preset load and less than a second preset load, further acquiring the outdoor environment temperature;
and controlling the second compressor and the fluorine pump to alternatively operate according to the actual demand load of the system and the outdoor environment temperature.
In a preferred technical solution of the above control method, the step of "controlling the second compressor and the fluorine pump to operate alternatively according to the actual demand load of the system and the outdoor ambient temperature" includes:
determining a third preset load according to the outdoor environment temperature;
and controlling the second compressor and the fluorine pump to alternatively operate according to the actual demand load of the system and the third preset load.
In a preferred technical solution of the above control method, the step of "controlling the second compressor and the fluorine pump to operate alternatively according to the actual demand load of the system and the third preset load" includes:
comparing the actual demand load of the system with the third preset load;
and controlling the second compressor and the fluorine pump to alternatively operate according to the comparison result of the actual demand load of the system and the third preset load.
In a preferred embodiment of the above control method, the step of controlling the second compressor and the fluorine pump to alternatively operate according to a comparison result between the actual demand load of the system and the third preset load includes:
and if the actual demand load of the system is less than or equal to the third preset load, controlling the fluorine pump to operate.
In a preferred embodiment of the above control method, the step of controlling the second compressor and the fluorine pump to alternatively operate according to a comparison result between the actual demand load of the system and the third preset load includes:
and if the actual demand load of the system is greater than the third preset load, controlling the second compressor to operate.
In a preferred embodiment of the above control method, the step of "determining a third preset load according to the outdoor ambient temperature" specifically includes:
under the condition that the fluorine pump runs, establishing a relation curve graph of a system energy efficiency ratio and an outdoor environment temperature, and recording the relation curve graph as a first energy efficiency curve graph;
under the condition that the second compressor is operated, establishing a relation curve graph of system energy efficiency ratio and outdoor environment temperature under different operation loads, and recording the relation curve graph as a second energy efficiency curve graph;
and determining the third preset load according to the outdoor environment temperature based on the first energy efficiency curve graph and the second energy efficiency curve graph.
In a preferred embodiment of the above control method, the step of controlling the second compressor and the fluorine pump to alternatively operate according to the actual demand load of the system further includes:
and if the actual demand load of the system is less than or equal to the first preset load, controlling the fluorine pump to operate.
In a preferred embodiment of the above control method, the step of controlling the second compressor and the fluorine pump to alternatively operate according to the actual demand load of the system further includes:
and if the actual demand load of the system is greater than or equal to the second preset load, controlling the second compressor to operate.
In a preferred technical solution of the above control method, the second preset load is a system rated load.
Under the condition of adopting the technical scheme, the high-pressure refrigerant circulation loop and the low-pressure refrigerant circulation loop exchange heat through the intermediate heat exchanger, and the fluorine pump is arranged in the low-pressure refrigerant circulation loop, so that the operation energy efficiency of the low-pressure refrigerant circulation loop can be effectively improved, and the operation energy efficiency of the cascade heat pump system is further improved; the control method can control the second compressor and the fluorine pump to operate alternatively according to the actual demand load of the system, so that the operation condition of the cascade heat pump system can be matched with the actual heat exchange demand of the cascade heat pump system all the time, the problem of low-efficiency operation is effectively avoided, the operation energy efficiency of the low-pressure refrigerant circulation loop can be effectively improved, and the operation energy efficiency of the whole cascade heat pump system can be effectively improved.
Drawings
Preferred embodiments of the present invention are described below in conjunction with the appended drawings, wherein:
FIG. 1 is a schematic diagram of the configuration of a cascade heat pump system of the present invention;
FIG. 2 is a flow chart of the main steps of the control method of the present invention;
FIG. 3 is a flow chart of the specific steps of a preferred embodiment of the control method of the present invention;
FIG. 4 is an energy efficiency curve of the system energy efficiency ratio versus the outdoor ambient temperature for different operating conditions of the cascade heat pump system of the present invention;
reference numerals:
1. a high pressure refrigerant circulation loop; 11. a first compressor; 12. a first heat exchanger; 13. a first throttle member; 14. an intermediate heat exchanger;
2. a low pressure refrigerant circulation loop; 21. a second compressor; 22. a fluorine pump; 23. a second throttling member; 24. a second heat exchanger; 25. a liquid storage member;
3. a first refrigerant circulation branch; 31. a first control valve;
4. a second refrigerant circulation branch; 41. a second control valve;
5. and a heat exchange water path.
Detailed Description
Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only for explaining the technical principle of the present invention, and are not intended to limit the scope of the present invention. And can be adjusted as needed by those skilled in the art to suit particular applications. For example, the cascade heat pump system described in the present invention may be a commercial cascade heat pump system, or an industrial cascade heat pump system, which is not limited to the above embodiments, and those skilled in the art can set the application of the cascade heat pump system according to the actual application requirements. Such changes in the application are within the scope of the present invention without departing from the basic concept thereof.
It should be noted that, in the description of the preferred embodiments, unless explicitly stated or limited otherwise, the terms "first", "second", and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Furthermore, the terms "connected" and "connecting" should be interpreted broadly, such as mechanically or electrically, directly or indirectly through intervening media, or internally to both elements, and thus should not be interpreted as limiting the scope of the present invention. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
Furthermore, it should be noted that in the description of the present invention, although the steps of the control method of the present invention are described in a specific order in the present application, the order is not limited, and those skilled in the art can perform the steps in a different order without departing from the basic principle of the present invention.
Referring first to fig. 1, fig. 1 is a schematic diagram of a cascade heat pump system according to the present invention. As shown in fig. 1, the cascade heat pump system of the present invention includes a high-pressure refrigerant circulation loop 1 and a low-pressure refrigerant circulation loop 2, wherein the high-pressure refrigerant circulation loop 1 is sequentially provided with a first compressor 11, a first heat exchanger 12, a first throttling member 13, and an intermediate heat exchanger 14, the low-pressure refrigerant circulation loop 2 is sequentially provided with a second compressor 21, the intermediate heat exchanger 14, a fluorine pump 22, a second throttling member 23, and a second heat exchanger 24, and the high-pressure refrigerant circulation loop 1 and the low-pressure refrigerant circulation loop 2 are configured to exchange heat through the intermediate heat exchanger 14.
First, it should be noted that the present invention does not limit the specific types of the refrigerants flowing in the high-pressure refrigerant circulation circuit 1 and the low-pressure refrigerant circulation circuit 2, and those skilled in the art can set the types according to actual situations. In a specific embodiment, the refrigerant in the high-pressure refrigerant circuit 1 is the refrigerant R134a, and the refrigerant in the low-pressure refrigerant circuit 2 is the refrigerant R410A.
It should be noted that the present invention does not limit the specific type of the intermediate heat exchanger 14, and it may be a shell-and-tube heat exchanger or a plate heat exchanger, and those skilled in the art can set the heat exchanger according to actual situations. In the present embodiment, the intermediate heat exchanger 14 is preferably a plate heat exchanger, so as to effectively improve the heat exchange efficiency of the refrigerant in the low-pressure refrigerant circulation circuit 2 in the intermediate heat exchanger 14.
Specifically, the intermediate heat exchanger 14 includes a housing, and a first heat exchange channel and a second heat exchange channel disposed in the housing, wherein the high-pressure refrigerant circulation loop 1 is communicated with the first heat exchange channel, so that the refrigerant in the high-pressure refrigerant circulation loop 1 flows through the first heat exchange channel, and the low-pressure refrigerant circulation loop 2 is communicated with the second heat exchange on/off, so that the refrigerant in the low-pressure refrigerant circulation loop 2 flows through the second heat exchange channel. As a preferred arrangement mode, the first heat exchange channels and the second heat exchange channels are arranged in a staggered manner, and the shell is further filled with a heat exchange medium, so that the heat exchange efficiency of the high-pressure refrigerant circulation loop 1 and the low-pressure refrigerant circulation loop 2 is effectively improved.
In addition, it should be noted that the present invention does not set any limitation to the specific structures and specific models of the first compressor 11, the second compressor 21, the fluorine pump 22, the first throttling member 13, the second throttling member 23, the first heat exchanger 12, and the second heat exchanger 24; the first compressor 11 and the second compressor 21 may be frequency conversion compressors or fixed frequency compressors, and preferably, both the first compressor 11 and the second compressor 21 are frequency conversion compressors so as to control the operation state of the cascade heat pump system; the fluorine pump 22 can be a fluorine-lined centrifugal pump, a fluorine-lined magnetic pump or a fluorine-lined self-priming pump; the first throttling component 13 and the second throttling component 23 can be electronic expansion valves, capillary tubes or thermal expansion valves; the first heat exchanger 12 and the second heat exchanger 24 may be plate heat exchangers or shell and tube heat exchangers, which are not restrictive and can be set by those skilled in the art according to the actual situation.
In addition, it should be noted that the present invention also does not limit the source of the heat source of the second heat exchanger 24, and it may be an air source or a ground source, which are not restrictive, as long as the purpose of exchanging heat with the second heat exchanger 24 can be achieved, and those skilled in the art can set the source according to the actual situation. In the preferred embodiment, the heat source of the second heat exchanger 24 is an air source to further reduce the energy consumption of the cascade heat pump system to improve the operation energy efficiency; specifically, the cascade heat pump system further includes a heat exchange fan (not shown in the figure), and the heat exchange fan is disposed near the second heat exchanger 24 to improve the heat exchange effect between the air and the refrigerant in the second heat exchanger 24.
Further, in this embodiment, the cascade heat pump system further includes a first refrigerant circulation branch 3, a first end of the first refrigerant circulation branch 3 is connected between the intermediate heat exchanger 14 and the fluorine pump 22, a second end of the first refrigerant circulation branch 3 is connected between the fluorine pump 22 and the second throttling component 23, and a first control valve 31 is disposed on the first refrigerant circulation branch 3. The first refrigerant circulation branch 3 and the first control valve 31 on the first refrigerant circulation branch 3 are arranged to selectively connect the fluorine pump 22 to the low-pressure refrigerant circulation loop 2, that is, the operation state of the fluorine pump 22 can be selectively controlled according to the actual operation condition of the cascade heat pump system, so as to further improve the operation energy efficiency of the cascade heat pump system.
Further preferably, the cascade heat pump system further includes a second refrigerant circulation branch 4, wherein a first end of the second refrigerant circulation branch 4 is connected between the second heat exchanger 24 and the second compressor 21, a second end of the second refrigerant circulation branch 4 is connected between the second compressor 21 and the intermediate heat exchanger 14, and a second control valve 41 is disposed on the second refrigerant circulation branch 4. The second refrigerant circulation branch 4 and the second control valve 41 on the second refrigerant circulation branch 4 are arranged to selectively connect the second compressor 21 to the low-pressure refrigerant circulation circuit 2, that is, to selectively control the operation state of the second compressor 21 according to the actual operation condition of the cascade heat pump system, so as to improve the operation energy efficiency of the cascade heat pump system to the maximum extent.
It should be noted that the present invention does not limit the specific structure and the specific type of the first control valve 31 and the second control valve 41, and the present invention may be an electromagnetic control valve, a hydraulic control valve, a one-way control valve, or a multi-way control valve, which are not restrictive, as long as the present invention can achieve the effect of controlling the on-off state of the first refrigerant circulation branch 3 and the second refrigerant circulation branch 4. Preferably, in the present embodiment, the first control valve 31 and the second control valve 41 are both one-way control valves, and the first one-way valve is configured to allow the refrigerant to flow from one side of the intermediate heat exchanger 14 to one side of the second throttling member 23 only, and the second one-way valve is configured to allow the refrigerant to flow from one side of the second heat exchanger 24 to one side of the intermediate heat exchanger 14 only, so as to further effectively ensure that the refrigerant does not flow backwards.
Preferably, in this embodiment, the low-pressure refrigerant circulation loop 2 is further provided with a liquid storage component 25, and the liquid storage component 25 is disposed between the intermediate heat exchanger 14 and the first end of the first refrigerant circulation branch 3; the arrangement of the liquid storage component 25 can effectively ensure the stability of the refrigerant flowing pressure in the low-pressure refrigerant circulation loop 2. It should be noted that the present invention does not limit the specific structure and the arrangement position of the liquid storage member 25, and those skilled in the art can set the configuration according to the actual situation.
Further, the high-pressure refrigerant circulation loop 1 is further provided with a first air separation device (not shown in the figure), and the first air separation device is arranged at an air inlet of the first compressor 11. The low-pressure refrigerant circulation circuit 2 is further provided with a second air separation device (not shown), which is disposed at an air inlet of the second compressor 21. First gas divides the device with the problem that the liquid attack can effectively be avoided first compressor 11 and second compressor 21 to appear easily in the setting of second gas divides the device, and then effectively guarantees first compressor 11 and second compressor 21's life. It should be noted that the present invention does not limit any specific type of the first gas separation device and the second gas separation device, and those skilled in the art can set the gas separation device according to actual situations.
In addition, in the preferred embodiment, the cascade heat pump system further includes a heat exchange water path 5, and a part of the heat exchange water path 5 is disposed in the first heat exchanger 12 to exchange heat with the refrigerant in the high-pressure refrigerant circulation circuit 1, so as to obtain high-temperature hot water. Of course, it should be noted that the present invention does not impose any limitation on the specific structure and use of the heat exchange water circuit 5, for example, it may be an open circuit, or it may be a circulation loop, it may be used for heat exchange for users, or it may be supplied for users, which is not limiting, and those skilled in the art may set itself according to the actual use requirement.
According to the cascade heat pump system, the fluorine pump 22 is arranged in the low-pressure refrigerant circulation loop 2, the use of the fluorine pump 22 and the use of the second compressor 21 can be switched according to the change of the ambient temperature, and the aim that the operation energy efficiency of the cascade heat pump system is still high under the large-span variable-environment working condition is fulfilled.
Further, the cascade heat pump system further includes an outdoor ambient temperature sensor capable of acquiring an ambient temperature in the vicinity of the cascade heat pump system, and a controller (not shown in the figure) capable of acquiring an ambient temperature detected by the outdoor ambient temperature sensor, and the controller is further capable of controlling the operation states and the like of the first control valve 31, the second control valve 41, the fluorine pump 22, and the second compressor 21, all of which are not restrictive. It should be noted that, the present invention does not set any limitation to the specific number and the setting position of the outdoor ambient temperature sensors, as long as the outdoor ambient temperature sensors can obtain the ambient temperature, and those skilled in the art can set the outdoor ambient temperature sensors according to actual situations. In addition, it can be understood by those skilled in the art that the present invention does not limit the specific structure and model of the controller, and the controller may be the original controller of the cascade heat pump system, or may be a controller separately configured to execute the control method of the present invention, and those skilled in the art can set the structure and model of the controller according to the actual use requirement.
Referring next to fig. 2, fig. 2 is a flow chart illustrating the main steps of the control method of the present invention. As shown in fig. 2, based on the cascade heat pump system described in the above embodiment, the control method of the present invention mainly includes the following steps:
s1: acquiring the actual demand load of the system;
s2: and controlling the second compressor and the fluorine pump to alternatively operate according to the actual demand load of the system.
In the case that the high-pressure refrigerant circulation circuit 1 is operated, that is, the cascade heat pump system needs to exchange heat, step S1 is executed first, that is, the controller obtains the actual demand load of the system. It should be noted that, the present invention does not limit any specific acquisition time and specific acquisition mode of the actual demand load of the system, and the present invention may directly acquire the actual demand load according to the data displayed by the cascade heat pump system, or calculate and acquire the actual demand load according to the current operating parameters of the cascade heat pump system, which are not restrictive, and those skilled in the art may set the actual demand load according to the actual situation.
Next, in step S2, the controller controls the second compressor 21 and the fluorine pump 22 to alternatively operate according to the actual demand load of the system. It should be noted that, the present invention does not set any limit to the specific control mode of the controller controlling the operation states of the second compressor 21 and the fluorine pump 22 according to the actual demand load of the system, for example, the controller may compare the actual demand load of the system with a preset load to control the second compressor 21 and the fluorine pump 22, or may bring the actual demand load of the system into a preset relational expression to determine whether the actual demand load meets the preset relation, so as to control the second compressor 21 and the fluorine pump 22; of course, this is not restrictive, and the skilled person can set itself according to the actual situation, and it is within the scope of the present invention to control the operation status of the second compressor 21 and the fluorine pump 22 according to the actual demand load of the system.
Referring next to fig. 3 and 4, fig. 3 is a flowchart illustrating specific steps of a preferred embodiment of the control method of the present invention, and fig. 4 is a graph illustrating energy efficiency ratio of the system versus outdoor ambient temperature of the cascade heat pump system of the present invention under different operating conditions; in the illustration of fig. 4, the "inverter press" is the second compressor 21 described in the above preferred embodiment. As shown in fig. 3 and 4, based on the cascade heat pump system described in the above embodiment, the control method of the preferred embodiment of the present invention includes the following steps:
s101: acquiring the actual demand load of the system;
s102: if the actual demand load of the system is greater than the first preset load and less than the second preset load, further acquiring the outdoor environment temperature;
s103: under the condition that a fluorine pump runs, establishing a relation curve graph of a system energy efficiency ratio and an outdoor environment temperature, and recording as a first energy efficiency curve graph;
s104: under the condition that the second compressor is operated, establishing a relation curve graph of the system energy efficiency ratio and the outdoor environment temperature under different operation loads, and recording the relation curve graph as a second energy efficiency curve graph;
s105: determining a third preset load according to the outdoor environment temperature based on the first energy efficiency curve graph and the second energy efficiency curve graph;
s106: comparing the actual demand load of the system with a third preset load;
s107: if the actual demand load of the system is less than or equal to a third preset load, controlling the fluorine pump to operate;
s108: if the actual demand load of the system is greater than a third preset load, controlling the second compressor to operate;
s109: if the actual demand load of the system is less than or equal to the first preset load, controlling the fluorine pump to operate;
s110: and controlling the second compressor to operate if the actual demand load of the system is greater than or equal to a second preset load.
In the case that the high-pressure refrigerant circulation circuit 1 is operated, that is, the cascade heat pump system needs to exchange heat, step S101 is executed first, that is, the controller obtains an actual demand load of the system. It should be noted that, the present invention does not limit any specific acquisition time and specific acquisition mode of the actual demand load of the system, and the present invention may directly acquire the actual demand load according to the data displayed by the cascade heat pump system, or calculate and acquire the actual demand load according to the current operating parameters of the cascade heat pump system, which are not restrictive, and those skilled in the art may set the actual demand load according to the actual situation.
Based on the obtained result of step S101, the controller can control the second compressor 21 and the fluorine pump 22 to alternatively operate according to the actual demand load of the system. It should be noted that, the present invention does not limit any specific control manner for the controller to control the operation states of the second compressor 21 and the fluorine pump 22 according to the actual demand load of the system, for example, the controller may compare the actual demand load of the system with a preset load to control the second compressor 21 and the fluorine pump 22, or may bring the actual demand load of the system into a preset relational expression to determine whether the actual demand load meets the preset relation, so as to control the second compressor 21 and the fluorine pump 22; of course, this is not restrictive, and the person skilled in the art can set the operation state according to the actual situation, and it is within the protection scope of the present invention as long as the operation state of the second compressor 21 and the fluorine pump 22 is controlled according to the actual demand load of the system.
As a preferable control manner, in step S102, if the actual demand load of the system is greater than a first preset load and less than a second preset load, the controller further obtains the outdoor ambient temperature detected by the temperature sensor; and jointly making a judgment according to the actual demand load of the system and the outdoor environment temperature, and correspondingly controlling the second compressor 21 and the fluorine pump 22 to alternatively operate based on the joint judgment result.
It should be noted that, the specific setting values of the first preset load and the second preset load are not limited in any way, and those skilled in the art can set the setting values according to the model and the actual operating condition of the cascade heat pump system. It should be noted that the present invention does not limit the specific control manner of the controller for controlling the operation states of the second compressor 21 and the fluorine pump 22 according to the actual demand load of the system and the outdoor ambient temperature, and the controller can be set by a person skilled in the art.
As a specific control mode, the controller may determine the third preset load according to the obtained outdoor environment temperature; of course, the present invention does not limit the specific determination method, and those skilled in the art can set the determination method according to actual needs. For example, a one-to-one mapping relationship may be established first, and then the only third preset load may be determined through the outdoor environment temperature; for another example, an image model may be created in the computer, and the unique third preset load may be determined by inputting the acquired outdoor ambient temperature into the image model.
Further, as a preferred determination method, the process of determining the third preset load according to the outdoor environment temperature specifically includes steps S103 to S104, and a graph of a relationship between the system energy efficiency ratio and the outdoor environment temperature is established and recorded as a first energy efficiency graph under the condition that the fluorine pump 22 is operated and the second compressor 21 is not operated; under the condition that the second compressor 21 is operated and the fluorine pump 22 is not operated, a relation graph of the system energy efficiency ratio and the outdoor environment temperature under different operation loads is established and recorded as a second energy efficiency graph. Next, in step S105, based on the first energy efficiency graph and the second energy efficiency graph, the controller determines the third preset load according to the outdoor environment temperature, so as to effectively improve accuracy of subsequent determination, and further improve heat exchange efficiency to the maximum extent.
It should be noted that, the specific execution order of step S103 and step S104 is not limited in any way, and step S103 and step S104 may be executed simultaneously or may be executed sequentially without being divided; the specific execution time of step S103 and step S104 is not limited in any way, and is preferably configured in the storage module of the controller directly before shipment, which is not restrictive, and can be set by a person skilled in the art according to actual situations.
Further preferably, in step S106, the controller compares the actual system demand load with the third preset load, and controls the second compressor 21 and the fluorine pump 22 to alternatively operate according to the comparison result between the actual system demand load and the third preset load. Based on the control mode, the actual operation condition of the cascade heat pump system can be matched with the heat exchange requirement all the time, and further the heat exchange efficiency is effectively improved.
Specifically, in step S107, if the actual system demand load is less than or equal to the third preset load, the controller controls the fluorine pump 22 to operate so as to effectively reduce the energy consumption while ensuring the heat exchange demand, and at this time, the first control valve 31 is closed and the second control valve 41 is opened. Further, in step S108, if the actual system demand load is greater than the third preset load, the controller controls the second compressor 21 to operate so as to effectively ensure the heat exchange efficiency of the cascade heat pump system, where the first control valve 31 is opened and the second control valve 41 is closed.
To further illustrate the above control logic, the content shown in fig. 4 is taken as an example to illustrate: as shown in fig. 4, the third preset load is a load at a crossing point of the first energy efficiency graph and the second energy efficiency graph at the same temperature.
For example, when the outdoor ambient temperature is T2, the third preset load is a load at an intersection (point a in fig. 4) of a curve of the fluorine pump system (the second energy efficiency graph) and a curve of the inverter press system (bkW) (the first energy efficiency graph) in fig. 4, that is, the third preset load is bkW. It is understood that the curve in the first energy efficiency curve chart can be countless based on different operation loads, so that at a certain ambient temperature, a variable frequency press system curve which can intersect with the fluorine pump system curve in fig. 4 can be always found, and the load value corresponding to the variable frequency press system curve is the third preset load. The ordinate values of the fluorine pump system curve and the variable frequency compressor system (bkW) curve in fig. 4 are energy efficiency ratios, and as can be seen from the content shown in fig. 4, in the case that the outdoor ambient temperature is T2, when the actual demand load of the system is less than or equal to bkW, the energy efficiency ratio of the cascade heat pump system when operating with the fluorine pump 22 is high, and when the actual demand load of the system is greater than bkW, the energy efficiency ratio of the cascade heat pump system when operating with the second compressor 21 is high, so that when the actual demand load of the system is less than or equal to the third preset load, the controller controls the operation of the fluorine pump 22; otherwise, the second compressor 21 is controlled to operate.
For another example, when the outdoor ambient temperature is T3, the third preset load is a load at an intersection (point B in fig. 4) of a curve of the fluorine pump system (the second energy efficiency graph) and a curve of the inverter press system (ckW) (the first energy efficiency graph) in fig. 4, that is, the third preset load is ckW. The ordinate values of the fluorine pump system curve and the variable frequency compressor system (ckW) curve in fig. 4 are energy efficiency ratios, and as can be seen from the content shown in fig. 4, in the case that the outdoor ambient temperature is T3, when the actual demand load of the system is less than or equal to ckW, the energy efficiency ratio of the cascade heat pump system when operating with the fluorine pump 22 is high, and when the actual demand load of the system is greater than ckW, the energy efficiency ratio of the cascade heat pump system when operating with the second compressor 21 is high, so that when the actual demand of the system is less than or equal to the third preset load, the controller controls the operation of the fluorine pump 22; otherwise, the second compressor 21 is controlled to operate.
In addition, as a preferable control manner, in step S109 and step S110, if the actual demand load of the system is less than or equal to the first preset load, the operation efficiency of the fluorine pump 22 is always higher than that of the second compressor 21, in this case, the controller directly controls the operation of the fluorine pump 22 without acquiring other parameters, so that the corresponding speed is effectively increased while the heat exchange efficiency is ensured; if the actual demand load of the system is greater than or equal to the second preset load, the operation efficiency of the second compressor 21 is always higher than that of the fluorine pump 22, in which case the controller directly controls the second compressor 21 to operate.
It should be noted that, the present invention does not limit any specific setting values of the first preset load and the second preset load, and those skilled in the art can set the setting values according to actual situations. Preferably, the second preset load is a rated load of the system, so as to ensure high operation energy efficiency of the cascade heat pump system to the maximum extent. Specifically, taking the system shown in fig. 4 as an example, the first preset load is akW, and the second preset load is dkW (rated load of the system), as can be seen from fig. 4, when the actual required load of the system is less than or equal to akW, the cascade heat pump system is operated with the highest energy efficiency regardless of the ambient temperature; when the actual demand load of the system is greater than or equal to dkW, the cascade heat pump system is most energy efficient when the second compressor 21 is operated regardless of the ambient temperature.
Based on the control logic, the invention can effectively avoid the phenomenon that the cascade heat pump system is frequently started and stopped, thereby effectively avoiding the problem that the cascade heat pump system is easy to be in an unstable operation state for a long time. The cascade heat pump system controls the second compressor 21 and the fluorine pump 22 to alternatively operate according to different loads and different outdoor environment temperatures, so that the start-up and shutdown period of the system is prolonged, the system operates on an optimal energy efficiency curve under any working condition, and the operation energy efficiency of the cascade heat pump system is effectively ensured.
So far, the technical solutions of the present invention have been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Equivalent changes or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the invention, and the technical scheme after the changes or substitutions can fall into the protection scope of the invention.
Claims (10)
1. The control method of the cascade heat pump system is characterized in that the cascade heat pump system comprises a high-pressure refrigerant circulation loop and a low-pressure refrigerant circulation loop, wherein a first compressor, a first heat exchanger, a first throttling component and an intermediate heat exchanger are arranged on the high-pressure refrigerant circulation loop, a second compressor, the intermediate heat exchanger, a fluorine pump, a second throttling component and a second heat exchanger are arranged on the low-pressure refrigerant circulation loop, the high-pressure refrigerant circulation loop and the low-pressure refrigerant circulation loop are arranged to exchange heat through the intermediate heat exchanger, and the second compressor and the fluorine pump are arranged to be capable of running alternatively;
under the condition that the high-pressure refrigerant circulating loop operates, the control method comprises the following steps:
acquiring the actual demand load of the system;
and controlling the second compressor and the fluorine pump to alternatively operate according to the actual demand load of the system.
2. The control method according to claim 1, wherein the step of controlling the second compressor and the fluorine pump to alternatively operate according to the actual demand load of the system specifically comprises:
if the actual demand load of the system is greater than a first preset load and less than a second preset load, further acquiring the outdoor environment temperature;
and controlling the second compressor and the fluorine pump to alternatively operate according to the actual demand load of the system and the outdoor environment temperature.
3. The control method according to claim 2, wherein the step of controlling the second compressor and the fluorine pump to alternatively operate according to the actual demand load of the system and the outdoor ambient temperature specifically comprises:
determining a third preset load according to the outdoor environment temperature;
and controlling the second compressor and the fluorine pump to alternatively operate according to the actual demand load of the system and the third preset load.
4. The control method according to claim 3, wherein the step of controlling the second compressor and the fluorine pump to operate alternatively according to the actual demand load of the system and the third preset load comprises:
comparing the actual demand load of the system with the third preset load;
and controlling the second compressor and the fluorine pump to alternatively operate according to the comparison result of the actual demand load of the system and the third preset load.
5. The control method according to claim 4, wherein the step of controlling the second compressor and the fluorine pump to operate alternatively in accordance with the comparison result between the actual demand load of the system and the third preset load comprises:
and if the actual demand load of the system is less than or equal to the third preset load, controlling the fluorine pump to operate.
6. The control method according to claim 4, wherein the step of controlling the second compressor and the fluorine pump to operate alternatively in accordance with the comparison result between the actual demand load of the system and the third preset load comprises:
and if the actual demand load of the system is greater than the third preset load, controlling the second compressor to operate.
7. The control method according to claim 3, wherein the step of determining a third preset load according to the outdoor ambient temperature specifically comprises:
under the condition that the fluorine pump runs, establishing a relation curve graph of a system energy efficiency ratio and an outdoor environment temperature, and recording the relation curve graph as a first energy efficiency curve graph;
under the condition that the second compressor is operated, establishing a relation curve graph of system energy efficiency ratio and outdoor environment temperature under different operation loads, and recording the relation curve graph as a second energy efficiency curve graph;
and determining the third preset load according to the outdoor environment temperature based on the first energy efficiency curve graph and the second energy efficiency curve graph.
8. The control method according to any one of claims 2 to 7, wherein the step of controlling the second compressor and the fluorine pump to operate alternatively in accordance with the actual demand load of the system further comprises:
and if the actual demand load of the system is less than or equal to the first preset load, controlling the fluorine pump to operate.
9. The control method according to any one of claims 2 to 7, wherein the step of controlling the second compressor and the fluorine pump to operate alternatively in accordance with the actual demand load of the system further comprises:
and if the actual demand load of the system is greater than or equal to the second preset load, controlling the second compressor to operate.
10. The control method according to any one of claims 2 to 7, characterized in that the second preset load is a system rated load.
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|---|---|---|---|
| CN202210471162.8A CN114941914B (en) | 2022-04-28 | Control method of cascade heat pump system |
Applications Claiming Priority (1)
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|---|---|---|---|
| CN202210471162.8A CN114941914B (en) | 2022-04-28 | Control method of cascade heat pump system |
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| CN114941914B CN114941914B (en) | 2024-07-09 |
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