CN114941914B - Control method of cascade heat pump system - Google Patents
Control method of cascade heat pump system Download PDFInfo
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- CN114941914B CN114941914B CN202210471162.8A CN202210471162A CN114941914B CN 114941914 B CN114941914 B CN 114941914B CN 202210471162 A CN202210471162 A CN 202210471162A CN 114941914 B CN114941914 B CN 114941914B
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- 238000000034 method Methods 0.000 title claims abstract description 32
- 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 76
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 76
- 239000011737 fluorine Substances 0.000 claims abstract description 76
- 239000007788 liquid Substances 0.000 description 7
- 238000000926 separation method Methods 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 230000007613 environmental effect Effects 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 4
- 238000004891 communication 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
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 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
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000013507 mapping Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000009987 spinning Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
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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
-
- 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
-
- 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
-
- 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)
- Thermal Sciences (AREA)
- Mechanical Engineering (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 to a control method of a cascade heat pump system, and aims to solve the problem of low operation energy efficiency of the existing cascade heat pump system. For this purpose, the cascade heat pump system of the invention comprises a high-pressure refrigerant circulation loop and a low-pressure refrigerant circulation loop, and 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 obtain 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 connected into the low-pressure refrigerant circulation loop according to actual conditions, so that the second compressor is effectively prevented from being in an operation state all the time, and further, the energy utilization rate of the system can be improved, and the operation 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
Along with the popularization of energy-saving and emission-reducing policies, more and more application occasions of high-temperature heat treatment by using a high-temperature heat pump system in industries such as food processing, spinning, chemical industry and the like are adopted. With the increasing demand of industrial heating, the application requirements of users on high-temperature heat pump systems are also increasing. First, the final heating temperature of high temperature heat pump systems generally needs to be greater than 70 ℃, and some even more than 90 ℃; second, the environmental conditions to which the high temperature heat pump system is applied are also very wide in span, the outdoor environmental temperature is from-30 ℃ to 35 ℃, and high temperature hot water or hot air needs to be provided both in winter and summer.
In particular, the high temperature hot water used in industry has a high temperature, which makes it difficult for a common heat pump system to meet the actual heating requirement, and the technology of the cascade heat pump system for providing high temperature hot water is very mature. The cascade heat pump system generally comprises a high-pressure refrigerant circulation loop and a low-pressure refrigerant circulation loop, and the high-pressure refrigerant circulation loop and the low-pressure refrigerant circulation loop exchange heat through a shared intermediate heat exchanger so as to achieve the purpose of providing high-temperature hot water. However, the existing cascade heat pump system still needs to perform cascade operation beyond the rated working condition, for example, when the outdoor ambient temperature is relatively high, that is, two-stage compression is still adopted under the working condition that the temperature difference between the evaporating temperature and the condensing temperature is small, and the adjustment flexibility of the setting mode is not high, so that the loss is large, and the operation energy efficiency of the cascade heat pump system is low, so that 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-mentioned technical problems.
Disclosure of Invention
The invention aims to solve the technical problem that the operation energy efficiency of the existing cascade heat pump system is low.
The invention provides a control method of a cascade heat pump system, which comprises a high-pressure refrigerant circulation loop and a low-pressure refrigerant circulation loop, wherein the high-pressure refrigerant circulation loop is provided with a first compressor, a first heat exchanger, a first throttling component and an intermediate heat exchanger, the low-pressure refrigerant circulation loop is provided with a second compressor, the intermediate heat exchanger, a fluorine pump, a second throttling component and a second heat exchanger, the high-pressure refrigerant circulation loop and the low-pressure refrigerant circulation loop are arranged to be capable of exchanging heat through the intermediate heat exchanger, and the second compressor and the fluorine pump are arranged to be capable of alternatively running;
under the condition that the high-pressure refrigerant circulation 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 operate alternatively according to the actual demand load of the system.
In the preferred technical solution of the above control method, the step of "controlling the second compressor and the fluorine pump to select one operation according to the actual demand load of the system" specifically includes:
If the actual demand load of the system is larger than the first preset load and smaller than the second preset load, further acquiring the outdoor environment temperature;
and controlling the second compressor and the fluorine pump to operate alternatively according to the actual demand load of the system and the outdoor environment temperature.
In the preferred technical solution of the above control method, the step of "controlling the second compressor and the fluorine pump to operate according to the actual demand load of the system and the outdoor ambient temperature" specifically includes:
determining a third preset load according to the outdoor environment temperature;
And 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.
In the preferred technical solution of the above control method, the step of controlling the second compressor and the fluorine pump to select one operation according to the actual demand load of the system and the third preset load specifically includes:
comparing the actual demand load of the system with the third preset load;
And controlling the second compressor and the fluorine pump to operate according to the comparison result of the actual demand load of the system and the third preset load.
In the 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 comparison result of the actual demand load of the system and the third preset load includes:
and if the actual demand load of the system is smaller than or equal to the third preset load, controlling the fluorine pump to run.
In the 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 comparison result of the actual demand load of the system and the third preset load includes:
and if the actual demand load of the system is larger than the third preset load, controlling the second compressor to run.
In a preferred technical solution of the above control method, the step of determining the third preset load according to the outdoor ambient temperature specifically includes:
under the condition that the fluorine pump operates, a relation curve graph of the energy efficiency ratio of the system and the outdoor environment temperature is established and is recorded as a first energy efficiency curve graph;
under the condition that the second compressor is operated, establishing a relation curve graph of the energy efficiency ratio of the system and the 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 technical solution of the above control method, the step of controlling the second compressor and the fluorine pump to select one operation according to the actual demand load of the system further includes:
And if the actual demand load of the system is smaller than or equal to the first preset load, controlling the fluorine pump to operate.
In a preferred technical solution of the above control method, the step of controlling the second compressor and the fluorine pump to select one operation 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 run.
In the preferred technical scheme of the control method, the second preset load is a rated load of the system.
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; according to the control method disclosed by the invention, one of the second compressor and the fluorine pump can be controlled to operate according to the actual demand load of the system, so that the operating condition of the cascade heat pump system can be always matched with the actual heat exchange demand of the cascade heat pump system, thereby effectively avoiding the problem of low-efficiency operation, and further effectively improving the operating energy efficiency of a low-pressure refrigerant circulation loop, so that the operating energy efficiency of the whole cascade heat pump system is effectively improved.
Drawings
Preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:
FIG. 1 is a schematic diagram of the structure of the 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 flowchart of the specific steps of a preferred embodiment of the control method of the present invention;
FIG. 4 is a graph of the energy efficiency ratio of the cascade heat pump system of the present invention versus outdoor ambient temperature under different operating conditions;
reference numerals:
1. A high-pressure refrigerant circulation circuit; 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 circuit; 21. a second compressor; 22. a fluorine pump; 23. a second throttle 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. A heat exchange waterway.
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 merely for explaining the technical principles of the present invention, and are not intended to limit the scope of the present invention. Those skilled in the art can adapt it as desired to suit a particular application. 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 limitative, and those skilled in the art can set the application of the cascade heat pump system according to the actual use requirement. Such changes in the application do not depart from the basic principles of the invention and are intended to be within the scope of the invention.
It should be noted that in the description of the preferred embodiments, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying any relative importance unless expressly specified or limited otherwise. Furthermore, the terms "coupled," "connected," and "connected" are used in a broad sense, and may be mechanically coupled, electrically coupled, directly coupled, indirectly coupled via an intervening medium, or internally coupled, and thus should not be construed as limiting the invention. The specific meaning of the above terms in the present invention can be understood by those skilled in the art according to the specific circumstances.
Furthermore, it should be noted that in the description of the present application, although the respective steps of the control method of the present application are described in a specific order in the present application, these orders are not limitative, but a person skilled in the art may perform the steps in a different order without departing from the basic principle of the present application.
Referring first to fig. 1, fig. 1 is a schematic structural 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 circuit 1 and a low-pressure refrigerant circulation circuit 2, wherein a first compressor 11, a first heat exchanger 12, a first throttle member 13 and an intermediate heat exchanger 14 are sequentially disposed on the high-pressure refrigerant circulation circuit 1, a second compressor 21, an intermediate heat exchanger 14, a fluorine pump 22, a second throttle member 23 and a second heat exchanger 24 are sequentially disposed on the low-pressure refrigerant circulation circuit 2, and the high-pressure refrigerant circulation circuit 1 and the low-pressure refrigerant circulation circuit 2 are disposed so as to be capable of exchanging 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 refrigerant according to the actual situation. As a specific embodiment, the refrigerant in the high-pressure refrigerant circulation circuit 1 is the refrigerant R134a, and the refrigerant in the low-pressure refrigerant circulation circuit 2 is the refrigerant R410A.
Furthermore, it should be noted that the present invention is not limited to the specific type of the intermediate heat exchanger 14, and may be a shell-and-tube heat exchanger or a plate heat exchanger, which may be set by those skilled in the art according to the actual situation. In this 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, where the high-pressure refrigerant circulation loop 1 is in communication 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 in communication with the second heat exchange channel, so that the refrigerant in the low-pressure refrigerant circulation loop 2 flows through the second heat exchange channel. As a preferable arrangement mode, the first heat exchange channels and the second heat exchange channels are staggered, and the shell is also filled with 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, 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 are not limited in the present invention; the first compressor 11 and the second compressor 21 may be variable frequency compressors or fixed frequency compressors, and preferably, the first compressor 11 and the second compressor 21 are variable frequency 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 and a fluorine-lined self-priming pump; the first throttling member 13 and the second throttling member 23 may 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 limitative, and may be set by those skilled in the art according to practical situations.
In addition, it should be noted that the heat source of the second heat exchanger 24 is not limited in the present invention, and may be an air source or a ground source, which is not limited, so long as the purpose of heat exchanging the second heat exchanger 24 can be achieved, and those skilled in the art can set the heat exchanger 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 increase the operating energy efficiency; specifically, the cascade heat pump system further includes a heat exchange fan (not shown in the drawing) disposed near the second heat exchanger 24 to enhance the heat exchange effect of 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 member 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 can selectively enable the fluorine pump 22 to be connected into 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 comprises 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 provided 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 can selectively enable the second compressor 21 to be connected into the low-pressure refrigerant circulation loop 2, that is, the operation state of the second compressor 21 can be selectively controlled 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 greatest extent.
The present invention is not limited to the specific structure and type of the first control valve 31 and the second control valve 41, and may be an electromagnetic control valve, a hydraulic control valve, a unidirectional control valve, or a multidirectional control valve, which are not limited as long as they have an effect of controlling the on-off states 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 check control valves, and the first check valve is configured to allow the refrigerant to flow from only one side of the intermediate heat exchanger 14 to one side of the second throttling member 23, and the second check valve is configured to allow the refrigerant to flow from only one side of the second heat exchanger 24 to one side of the intermediate heat exchanger 14, so as to further effectively ensure that the refrigerant does not flow backward.
Preferably, in the present embodiment, the low-pressure refrigerant circulation circuit 2 is further provided with a liquid storage member 25, and the liquid storage member 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 cold flow pressure in the low-pressure refrigerant circulation loop 2. It should be noted that the specific structure and the arrangement position of the liquid storage member 25 are not limited in the present invention, and those skilled in the art can set the liquid storage member according to the actual situation.
Further, the high-pressure refrigerant circulation circuit 1 is further provided with a first air separation device (not shown in the figure), and the first air separation device is disposed at the air inlet of the first compressor 11. The low-pressure refrigerant circulation circuit 2 is further provided with a second gas separation device (not shown in the figure), which is disposed at the gas inlet of the second compressor 21. The first air separation device and the second air separation device can effectively avoid the problem that the first compressor 11 and the second compressor 21 are easy to generate liquid impact, and further effectively ensure the service lives of the first compressor 11 and the second compressor 21. It should be noted that the specific types of the first gas separation device and the second gas separation device are not limited in the present invention, and may be set by those skilled in the art according to the actual situation.
Furthermore, 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 specific structure and use of the heat exchange waterway 5 are not limited, for example, it may be an open circuit, or may be a circulation loop, which may be used for heat exchange for a user, or may be used for a user, which is not limited, and may be set by a person skilled in the art according to actual use requirements.
According to the cascade heat pump system, the fluorine pump 22 is arranged in the low-pressure refrigerant circulation loop 2, so that the use of the fluorine pump 22 and the second compressor 21 can be switched according to the change of the ambient temperature, and the purpose that the operation energy efficiency of the cascade heat pump system is still higher under the long-span variable-ambient working condition is achieved.
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 drawing) capable of acquiring an ambient temperature detected by the outdoor ambient temperature sensor, and the controller is also capable of controlling the operation states of the first control valve 31, the second control valve 41, the fluorine pump 22, the second compressor 21, and the like, which are not limitative. It should be noted that, the present invention does not limit the specific number and positions of the outdoor environmental temperature sensors, so long as they can obtain the environmental temperature, and those skilled in the art can set the outdoor environmental temperature sensors according to the actual situation. In addition, it will 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 an original controller of the cascade heat pump system or a controller separately provided for executing the control method of the present invention, and those skilled in the art may set the structure and model of the controller according to actual use requirements.
Referring next to fig. 2, fig. 2 is a flow chart of 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 operate according to the actual demand load of the system.
Under the condition that the high-pressure refrigerant circulation loop 1 is operated, namely, the cascade heat pump system needs to exchange heat, firstly, the step S1 is executed, namely, the controller obtains the actual demand load of the system. It should be noted that, the present invention does not limit the specific acquisition time and the specific acquisition mode of the actual demand load of the system, and the specific acquisition time and the specific acquisition mode can be directly acquired according to the data displayed by the cascade heat pump system, or can be calculated and acquired according to the current operation parameters of the cascade heat pump system, which are not limiting, and can be set by a person skilled in the art according to the actual situation.
Next, in step S2, the controller controls the second compressor 21 and the fluorine pump 22 to operate alternatively according to the actual demand load of the system. It should be noted that, the present invention does not limit the specific control manner of 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 the 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 of the system satisfies the preset relation, so as to control the second compressor 21 and the fluorine pump 22; of course, this is not limitative, and a person skilled in the art can set it according to the actual situation, so long as the operation states of the second compressor 21 and the fluorine pump 22 are controlled according to the actual demand load of the system, which shall fall within the protection scope of the present invention.
Referring next to fig. 3 and 4, fig. 3 is a flowchart showing the specific steps of a preferred embodiment of the control method of the present invention, and fig. 4 is a graph showing the energy efficiency ratio of the cascade heat pump system of the present invention versus the outdoor ambient temperature 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 steps of:
S101: acquiring the actual demand load of the system;
S102: if the actual demand load of the system is larger than the first preset load and smaller than the second preset load, further acquiring the outdoor environment temperature;
S103: under the condition that the fluorine pump operates, a relation curve graph of the energy efficiency ratio of the system and the outdoor environment temperature is established and is recorded as a first energy efficiency curve graph;
S104: under the condition that the second compressor is operated, establishing a relation graph of the energy efficiency ratio of the system and the outdoor environment temperature under different operation loads, and recording the relation graph as a second energy efficiency 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 smaller than or equal to the third preset load, controlling the fluorine pump to operate;
s108: if the actual demand load of the system is larger than the third preset load, controlling the second compressor to run;
s109: if the actual demand load of the system is smaller than or equal to the first preset load, controlling the fluorine pump to operate;
s110: and if the actual demand load of the system is greater than or equal to the second preset load, controlling the second compressor to run.
Under the condition that the high-pressure refrigerant circulation loop 1 is running, that is, under the condition that the cascade heat pump system needs to perform heat exchange, firstly, step S101 is executed, that is, the controller obtains the actual demand load of the system. It should be noted that, the present invention does not limit the specific acquisition time and the specific acquisition mode of the actual demand load of the system, and the specific acquisition time and the specific acquisition mode can be directly acquired according to the data displayed by the cascade heat pump system, or can be calculated and acquired according to the current operation parameters of the cascade heat pump system, which are not limiting, and can be set by a person skilled in the art according to the actual situation.
Based on the obtained result in step S101, the controller can control the second compressor 21 and the fluorine pump 22 to operate alternatively according to the actual demand load of the system. It should be noted that, the present invention does not limit the specific control manner of 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 the 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 of the system satisfies the preset relation, so as to control the second compressor 21 and the fluorine pump 22; of course, this is not limitative, and a person skilled in the art can set it according to the actual situation, so long as the operation states of the second compressor 21 and the fluorine pump 22 are controlled according to the actual demand load of the system, which shall fall within the protection scope of the present invention.
As a preferred control manner, in step S102, if the system actual demand load is greater than a first preset load and less than a second preset load, the controller further acquires the outdoor ambient temperature detected by the temperature sensor; and jointly judging 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 operate alternatively based on the result of the jointly judging.
It should be noted that, the specific setting values of the first preset load and the second preset load are not limited in the present invention, and a person skilled in the art may set the specific setting values according to the model and the actual running situation of the cascade heat pump system. In addition, it should be noted that the present invention also does not limit the specific control manner of 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 and the outdoor environment temperature, and the present invention can be set by those skilled in the art.
As a specific control manner, the controller can determine the third preset load according to the obtained outdoor environment temperature; of course, the present invention is not limited to the specific determination modes described above, and those skilled in the art can set the specific determination modes according to actual use requirements. For example, a one-to-one mapping relationship may be established first, and then a unique third preset load may be determined by the outdoor ambient temperature; for another example, an image model may be first built in the computer, and the unique third preset load may be determined by inputting the acquired outdoor environment temperature into the image model.
Further, as a preferable determination manner, the process of determining the third preset load according to the outdoor environment temperature specifically includes steps S103 to S104, and in the case that the fluorine pump 22 is operated and the second compressor 21 is not operated, a relationship graph of the system energy efficiency ratio and the outdoor environment temperature is established and is recorded as a first energy efficiency graph; in the case where the second compressor 21 is operated and the fluorine pump 22 is not operated, a relationship graph of the system energy efficiency ratio and the outdoor ambient temperature at different operating loads is established, and is noted 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 the accuracy of the subsequent judgment, and further improve the heat exchange efficiency to the greatest extent.
It should be noted that, the specific execution sequence of the step S103 and the step S104 is not limited in the present invention, and the step S103 and the step S104 may be executed simultaneously or sequentially without being sequenced; the specific execution time of step S103 and step S104 is not limited, and is preferably configured in the memory module of the controller directly before shipment, which is not limited, 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 of the actual system demand load and the third preset load. Based on the control mode, the actual running condition of the cascade heat pump system can be always matched with the heat exchange requirement of the cascade heat pump system, and therefore the heat exchange efficiency is effectively improved.
Specifically, in step S107, if the actual demand load of the system 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 demand load of the system 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, and at this time, the first control valve 31 is opened and the second control valve 41 is closed.
To further illustrate the control logic, consider the example shown in fig. 4: as shown in fig. 4, the third preset load is the load at the intersection 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 the load at the intersection (point a in fig. 4) of the fluorine pump system curve (the second energy efficiency curve) and the variable frequency press system (bkW) curve (the first energy efficiency curve) in fig. 4, that is, the third preset load is bkW. It will be appreciated that, based on different operating loads, the curves in the first energy efficiency graph may be innumerable, so that, at a certain ambient temperature, a variable frequency press system curve that can intersect 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 press system (bkW) curve in fig. 4 are energy efficiency ratios, and as can be seen from the description 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 is high when the fluorine pump 22 is operated, and when the actual demand load of the system is greater than bkW, the energy efficiency ratio of the cascade heat pump system is high when the second compressor 21 is operated, so that when the actual demand load of the system is less than or equal to the third preset load, the controller controls the fluorine pump 22 to operate; and conversely, the second compressor 21 is controlled to operate.
For another example, when the outdoor ambient temperature is T3, the third preset load is the load at the intersection (point B in fig. 4) of the fluorine pump system curve (the second energy efficiency curve) and the variable frequency press system (ckW) curve (the first energy efficiency curve) in fig. 4, that is, the third preset load is ckW. The ordinate values of the fluorine pump system curve and the variable frequency press system (ckW) curve in fig. 4 are energy efficiency ratios, and as can be seen from the description shown in fig. 4, in the case that the outdoor environment 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 is high when the fluorine pump 22 is operated, and when the actual demand load of the system is greater than ckW, the energy efficiency ratio of the cascade heat pump system is high when the second compressor 21 is operated, so that when the actual demand of the system is less than or equal to the third preset load, the controller controls the fluorine pump 22 to operate; and conversely, the second compressor 21 is controlled to operate.
In addition, as a preferred 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 which 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 specific setting values of the first preset load and the second preset load are not limited in the present invention, and may be set by a person skilled in the art according to the actual situation. Preferably, the second preset load is a system rated load so as to ensure high operation energy efficiency of the cascade heat pump system to the greatest extent. Specifically, taking the system shown in fig. 4 as an example, the first preset load is akW, the second preset load is dkW (the rated load of the system), as can be seen from fig. 4, when the actual demand load of the system is less than or equal to akW, the cascade heat pump system is the most energy-efficient when operated with the fluorine pump 22, regardless of the ambient temperature; and when the actual demand load of the system is larger than or equal to dkW, the cascade heat pump system has the highest energy efficiency when the second compressor 21 is operated no matter what the ambient temperature is.
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 running state for a long time. According to the cascade heat pump system, the second compressor 21 and the fluorine pump 22 are controlled to operate alternatively according to different loads and different outdoor environment temperatures, the start-stop 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.
Thus far, the technical solution of the present invention has 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 protection of the present invention is not limited to these specific embodiments. Equivalent modifications and substitutions for related technical features may be made by those skilled in the art without departing from the principles of the present invention, and such modifications and substitutions will fall within the scope of the present invention.
Claims (5)
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 be capable of exchanging heat through the intermediate heat exchanger, and the second compressor and the fluorine pump are arranged to be capable of alternatively running;
under the condition that the high-pressure refrigerant circulation loop operates, the control method comprises the following steps:
acquiring the actual demand load of the system;
controlling the second compressor and the fluorine pump to operate alternatively according to the actual demand load of the system; wherein,
If the actual demand load of the system is larger than the first preset load and smaller than the second preset load, further acquiring the outdoor environment temperature;
determining a third preset load according to the outdoor environment temperature;
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;
if the actual demand load of the system is smaller than or equal to the first preset load, controlling the fluorine pump to operate;
if the actual demand load of the system is greater than or equal to the second preset load, controlling the second compressor to run;
Wherein, the determining a third preset load according to the outdoor environment temperature includes:
under the condition that the fluorine pump operates, a relation curve graph of the energy efficiency ratio of the system and the outdoor environment temperature is established and is recorded as a first energy efficiency curve graph;
under the condition that the second compressor is operated, establishing a relation curve graph of the energy efficiency ratio of the system and the 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.
2. The control method according to claim 1, wherein the step of controlling the operation of the second compressor and the fluorine pump 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 operate according to the comparison result of the actual demand load of the system and the third preset load.
3. The control method according to claim 2, wherein the step of controlling the second compressor and the fluorine pump to operate in accordance with the comparison result of the actual demand load of the system and the third preset load includes:
and if the actual demand load of the system is smaller than or equal to the third preset load, controlling the fluorine pump to run.
4. The control method according to claim 2, wherein the step of controlling the second compressor and the fluorine pump to operate in accordance with the comparison result of the actual demand load of the system and the third preset load includes:
and if the actual demand load of the system is larger than the third preset load, controlling the second compressor to run.
5. The control method according to any one of claims 1 to 4, characterized in that the second preset load is a system rated load.
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| CN101280976A (en) * | 2008-05-30 | 2008-10-08 | 天津商业大学 | CO2/NH3 combined refrigeration system |
| CN202074749U (en) * | 2011-06-08 | 2011-12-14 | 四川依米康环境科技股份有限公司 | Energy-saving air conditioning unit with double power source pumps |
| CN110657597B (en) * | 2019-11-01 | 2023-07-25 | 深圳市艾特网能技术有限公司 | Fluorine pump multi-connected refrigerating system and control method thereof |
| CN111043781A (en) * | 2019-12-13 | 2020-04-21 | 华为技术有限公司 | Compressor and fluorine pump combined air conditioning system |
| CN111442552A (en) * | 2020-05-11 | 2020-07-24 | 珠海格力电器股份有限公司 | Cascade type refrigerant circulating system, air conditioning equipment and control method of cascade type refrigerant circulating system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN201561600U (en) * | 2009-04-24 | 2010-08-25 | 济源市贝迪地能中央空调设备有限公司 | Ultra low temperature overlapping unit |
| CN112682910A (en) * | 2020-12-08 | 2021-04-20 | 珠海格力电器股份有限公司 | Method and system for switching operation modes of dual-power cooling system |
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