Refrigeration plant room energy-saving control system and method based on water pump frequency modulation

Abstract

The application discloses a kind of refrigeration plant energy-saving control system and method based on water pump frequency modulation, specifically related to industrial water pump frequency conversion technical field, the system includes cooling tower, cooling water pump, refrigeration unit, refrigerated water pump, central air conditioning terminal and intelligent remote control system, cooling tower is connected with refrigeration unit by cooling water pipeline, cooling water pump is connected with cooling water pipeline;Refrigeration unit is connected with central air conditioning terminal by refrigerated water pipeline, refrigerated water pump is connected with refrigerated water pipeline, and cooling water pipeline, refrigerated water pipeline are respectively provided with cooling water pipeline flowmeter and refrigerated water pipeline flowmeter;Refrigerated water pipeline flowmeter, cooling water pipeline flowmeter, cooling water pump, refrigerated water pump and central air conditioning terminal are connected with intelligent remote control system.The application can effectively avoid the unnecessary loss of energy, reduce the power consumption of water pump, realize significant energy-saving effect, improve overall operation efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial water pump frequency conversion and the field of central air conditioning energy saving, and in particular to a refrigeration machine room energy saving control system and method based on water pump frequency modulation. BACKGROUND

[0002] Under the background of increasing emphasis on energy saving and emission reduction and sustainable development in the world and China, building energy consumption problems are becoming increasingly prominent. Among them, the central air conditioning system, as an important part of building energy consumption, has a significant proportion of energy consumption, especially the refrigeration machine room, as the core part of the central air conditioning system, its operation efficiency is directly related to the energy consumption level of the whole system. However, the traditional refrigeration machine room has many deficiencies in equipment selection, system design and operation control, such as unreasonable equipment selection, poor system matching, low operation efficiency and serious energy waste, etc., which seriously restricts the improvement of the overall energy efficiency of the central air conditioning system.

[0003] At present, there are still the following deficiencies in the energy saving optimization of refrigeration machine rooms in China:

[0004] (1) Water pump frequency modulation and central air conditioning terminal load rate cannot be accurately linked in real time.

[0005] In the refrigeration machine room, the water pump frequency modulation and the central air conditioning terminal load rate cannot be accurately linked in real time, which leads to the limitation of energy efficiency optimization. Due to the delay of information transmission between systems, the imperfection of control strategy or the compatibility problem of equipment, the water pump frequency modulation often cannot quickly respond to the change of terminal load rate, thereby affecting the operation efficiency and energy saving effect of the whole refrigeration system. For example, Chinese invention patent CN117781562A uses a frequency converter to calculate the frequency through sensor data, changes the water pump speed, and Chinese invention patent CN114992783A adopts intelligent linkage between central air conditioning terminal and refrigeration machine room. However, the above patent solutions do not specifically consider the real-time accurate linkage of central air conditioning terminal load rate and water pump frequency modulation technology, which cannot make the water pump maintain a low-power high-efficiency operation state, and cannot achieve high-efficiency energy saving effect.

[0006] (2) Centrifugal pump stops, and water cannot be completely drained due to its special structure.

[0007] When the refrigeration machine room stops, the water pump needs to stop and drain water. The existing technology is to install a drain valve below the water pump to drain water. Due to the internal structure characteristics of the centrifugal pump, such as the gap between the impeller and the pump shell, the design of the sealing element and the complexity of the pipeline connection, water cannot be completely drained during the drainage process. The residual water may rust the equipment, affect the performance and service life of the centrifugal pump. For example, Chinese utility model patent CN219605619U drains the internal water through the drain port below the centrifugal pump, without considering that the special internal structure of the centrifugal pump may cause water residue. SUMMARY

[0008] The present application aims to at least partly solve one of the above technical problems in the prior art, and provides a refrigeration plant energy-saving control system and method based on water pump frequency modulation.

[0009] To achieve the object of the present application, the present application provides a refrigeration plant energy-saving control system based on water pump frequency modulation, which comprises a cooling tower, a cooling water pump, a refrigeration unit, a chilled water pump, a central air conditioning terminal and an intelligent remote control system,

[0010] The cooling tower is connected with the refrigeration unit through a cooling water pipeline, and the cooling water pump is connected with the cooling water pipeline.

[0011] The refrigeration unit is connected with the central air conditioning terminal through a chilled water pipeline, and the chilled water pump is connected with the chilled water pipeline.

[0012] The chilled water pipeline flow meter, the cooling water pipeline flow meter, the cooling water pump, the chilled water pump and the central air conditioning terminal are all connected with the intelligent remote control system, and the cooling water pump, the chilled water pump and the central air conditioning terminal realize real-time accurate linkage through the intelligent remote control system.

[0013] Preferably, the cooling water pipeline comprises a cooling water supply pipeline and a cooling water outlet pipeline, the cooling tower and the refrigeration unit are connected to form a loop through the cooling water supply pipeline and the cooling water outlet pipeline, the cooling water pump is connected with the cooling water supply pipeline, and the cooling water pipeline flow meter is arranged on the cooling water supply pipeline.

[0014] That is, the cooling tower is connected with the cooling water supply pipeline; the cooling tower is connected with the cooling water outlet pipeline; the central air conditioning terminal is connected with the chilled water supply pipeline; the central air conditioning terminal is connected with the chilled water outlet pipeline; the refrigeration unit is connected with the cooling water supply pipeline; the refrigeration unit is connected with the cooling water outlet pipeline; the refrigeration unit is connected with the chilled water supply pipeline; and the refrigeration unit is connected with the chilled water outlet pipeline.

[0015] Preferably, a cooling water gas pump is further arranged, and the cooling water gas pump is connected with the water inlet of the cooling water pump through a pipeline. The cooling water gas pump is connected with the water inlet of the cooling water pump through a hose, and when the centrifuge is stopped, the gas pump is connected with compressed air, so that the residual liquid in the pump is effectively discharged by using the pressure difference, the overall operation efficiency is improved, and the energy-saving effect is achieved.

[0016] The cooling water pump is connected with the cooling water supply pipeline.

[0017] Preferably, the pipeline is a hose.

[0018] Preferably, the chilled water pipeline comprises a chilled water supply pipeline and a chilled water outlet pipeline, the refrigeration unit and the central air conditioning terminal are connected to form a loop through the chilled water supply pipeline and the chilled water outlet pipeline, the chilled water pump is connected with the chilled water supply pipeline, and the chilled water pipeline flow meter is arranged on the chilled water supply pipeline.

[0019] Preferably, a chilled water gas pump is further arranged, and the chilled water gas pump is connected with the water inlet of the chilled water pump through a pipeline. The chilled water gas pump is connected with the water inlet of the chilled water pump through a hose. When the centrifugal machine is stopped, the gas pump is connected with compressed air, and the residual liquid in the pump is effectively discharged in time by using the pressure difference, so that the overall operation efficiency is improved, and the energy saving effect is achieved.

[0020] The chilled water pump is connected with the chilled water supply pipeline.

[0021] The application further provides a refrigeration plant room energy saving control method based on pump frequency modulation, which is realized based on the foregoing system, and comprises the following steps:

[0022] In step S1, the intelligent remote control system monitors the load rate of the central air conditioning terminal.

[0023] In step S2, the intelligent remote control system calculates the required flow of the cooling water and the chilled water according to the load rate, and outputs a cooling water and chilled water flow demand signal F1 to the cooling water pump and the chilled water pump.

[0024] In step S3, the cooling water pump and the chilled water pump are frequency-modulated according to the flow demand to reach a required rotating speed n.

[0025] In step S4, the intelligent remote control system monitors the flow on the corresponding pipeline through the cooling water pipeline flow meter and the chilled water pipeline flow meter.

[0026] In step S5, if the flow after frequency modulation meets the refrigeration demand, the terminal demand is met; otherwise, step S3 is repeated for frequency modulation until the flow demand is met, and the energy saving effect is achieved.

[0027] Preferably, in step S3, the cooling water pump and the chilled water pump are matched to the water pump frequency of the cooling water pump and the chilled water pump in the water pump characteristic curve of the cooling water pump and the chilled water pump by combining the required flow of the cooling water and the chilled water in step S2, and the rotating speed of the corresponding pump is adjusted based on the water pump frequency.

[0028] Preferably, when matching the water pump frequency, the difference value AF is obtained by subtracting the chilled water and refrigerated water flow demand signal F1 from the existing chilled water and refrigerated water flow signal F2, and the low-power high-efficiency point is matched according to the chilled water and refrigerated water flow demand signal F1 and the difference value AF, in combination with the efficiency, shaft power and flow relationship curve in the water pump characteristic curve, and the water pump frequency corresponding to the low-power high-efficiency point is the required water pump frequency f.

[0029] Preferably, in steps S4-S5, the flow after frequency adjustment is monitored by the chilled water pipeline flow meter and the refrigerated water pipeline flow meter, and it is judged whether the flow after frequency adjustment is equal to the chilled water and refrigerated water flow demand signal F1, if not, the low-power high-efficiency point is matched again through the water pump characteristic curve to achieve the chilled water and refrigerated water flow demand signal F1, to meet the central air conditioning terminal refrigeration demand and achieve the refrigeration demand, otherwise, it is ended.

[0030] Compared with the prior art, the beneficial effects of the present application include:

[0031] (1) The refrigeration machine room energy-saving control system and method based on water pump frequency adjustment can calculate the required flow of chilled water and refrigerated water according to the terminal load rate change through the intelligent remote control system, and then match the required water pump frequency through the water pump characteristic curve and flow calculation, and adjust the water pump speed through the frequency converter, which not only meets the flow demand, but also reduces the energy consumption of the water pump, improves the economic benefit, and achieves the energy-saving effect.

[0032] (2) The real-time and accurate linkage of water pump frequency adjustment and central air conditioning terminal load rate can ensure that the operating frequency of the water pump closely matches the actual load demand of the central air conditioning, thereby realizing the maximum utilization of energy. Specifically, when the terminal load rate of the central air conditioning increases, the water pump frequency adjustment system can automatically increase the operating frequency of the water pump to meet the increased cooling demand, and vice versa, when the load rate decreases, the water pump operating frequency will also be adjusted accordingly to avoid unnecessary energy waste. This real-time linkage method not only improves the response speed and adjustment accuracy of the system, but also significantly reduces the energy consumption and prolongs the service life of the equipment, providing a more comfortable and energy-saving indoor environment for buildings. At the same time, it also reflects the development trend of modern building intelligence and greenization, and has important significance for promoting energy saving and emission reduction and realizing sustainable development.

[0033] (3) The advantage of using air pump to discharge the residual liquid of centrifugal pump lies in its high efficiency and significant protection of equipment. The air pump can effectively discharge the residual liquid in the centrifugal pump by introducing compressed air into the interior of the centrifugal pump, using the pressure difference to remove the residual water in the pump body quickly and relatively completely, avoiding the problems of rust and corrosion caused by long-term water accumulation, thereby protecting the internal structure and key components of the centrifugal pump and prolonging the service life of the equipment. In addition, using air pump to drain water also reduces the cumbersome work and possible mechanical damage caused by disassembling the pump body for drainage, improving maintenance efficiency and safety. Therefore, using air pump to discharge the residual liquid of centrifugal pump is an economical and practical maintenance method. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a structure diagram of a refrigeration plant room energy-saving control system based on water pump frequency modulation according to an embodiment of the present application;

[0035] Figure 2 is a water pump frequency modulation step diagram in the embodiment of the present application;

[0036] Figure 3 is a water pump frequency modulation principle diagram in the embodiment of the present application;

[0037] In the figure: 1. Cooling tower; 2. Cooling water pump; 3. Cooling water supply pipeline; 4. Refrigeration unit; 5. Chilled water supply pipeline; 6. Chilled water pump; 7. Central air conditioning terminal; 8. Chilled water outlet pipeline; 9. Chilled water pipeline flow meter; 10. Cooling water pipeline flow meter; 11. Cooling water outlet pipeline; 12. Intelligent remote control system; 21. Cooling water gas pump; 22. Chilled water gas pump. DETAILED DESCRIPTION

[0038] This part will describe the specific embodiments of the present application in detail, and the preferred embodiments of the present application are shown in the accompanying drawings, which serve to supplement the description in the text part of the specification and enable people to intuitively and visually understand each technical feature and the overall technical solution of the present application, but it cannot be understood as a limitation on the protection scope of the present application.

[0039] As Figure 1As shown, the application provides a refrigeration plant energy-saving control system based on water pump frequency modulation, which comprises a cooling tower 1, a cooling water pump 2, a cooling water supply pipeline 3, a refrigeration unit 4, a chilled water supply pipeline 5, a chilled water pump 6, a central air conditioning terminal 7, a chilled water outlet pipeline 8, a chilled water pipeline flow meter 9, a cooling water pipeline flow meter 10, a cooling water outlet pipeline 11, an intelligent remote control system 12, a cooling water gas pump 21 and a chilled water gas pump 22. The cooling tower 1 is connected with the cooling water supply pipeline 3 and the cooling water outlet pipeline 11, so as to provide cooling water and cool the cooling water. The chilled water supply pipeline 5 and the chilled water outlet pipeline 8 are both connected with the central air conditioning terminal 7, so as to transport chilled water to provide cold energy for the central air conditioning terminal 7.

[0040] The cooling water pump 2 is connected with the cooling water supply pipeline 3, and the chilled water pump 6 is connected with the chilled water supply pipeline 5. The water pump frequency modulation is used to change the rotating speed, so as to change the water delivery capacity, meet the terminal requirements and achieve the energy-saving effect.

[0041] The refrigeration unit 4 is connected with the cooling water supply pipeline 3, the cooling water outlet pipeline 11, the chilled water supply pipeline 5 and the chilled water outlet pipeline 8. The refrigerant is used in the refrigeration unit 4 to indirectly exchange heat between the cooling water and the chilled water, so as to reduce the chilled water to the set temperature and meet the cooling supply requirements.

[0042] The cooling water pipeline flow meter 10 is installed on the cooling water supply pipeline 3, and the chilled water pipeline flow meter 9 is installed on the chilled water supply pipeline 5. The cooling water pipeline flow meter 10 and the chilled water pipeline flow meter 9 are both electrically connected with the intelligent remote control system 12, so as to monitor the flow of the cooling water and the chilled water. After the water pump frequency modulation, whether the flow of the cooling water and the chilled water meets the set value is monitored, so as to provide feedback adjustment.

[0043] In some embodiments of the application, the cooling water gas pump 21 is connected with the water inlet of the cooling water pump 2 through a hose, and the chilled water gas pump 22 is connected with the water inlet of the chilled water pump 6 through a hose. When the refrigeration plant is stopped, compressed air is introduced into the cooling water gas pump 21 and the chilled water gas pump 22. The air pressure difference is used to effectively discharge the residual liquid in the cooling water pump 2 and the chilled water pump 6, so as to avoid the rust and corrosion problems caused by long-time water accumulation, thereby protecting the internal structure and key components of the centrifugal pump, prolonging the service life, improving the water pump operation efficiency and achieving the energy-saving effect.

[0044] The application provides a refrigeration plant energy-saving control method based on water pump frequency modulation, which specifically comprises the following steps:

[0045] Step S1, the intelligent remote control system 12 monitors the load rate of the central air conditioning terminal 7.

[0046] Step S2, the intelligent remote control system 12 calculates the required flow of cooling water and chilled water through the load rate, and transmits the cooling water and chilled water flow demand signal F1 to the cooling water pump 2 and the chilled water pump 6, wherein the cooling water and chilled water flow demand signal F1 includes a cooling water flow demand signal and a chilled water flow demand signal;

[0047] Step S3, the cooling water pump 2 and the chilled water pump 6 are frequency-regulated according to the corresponding flow demand signal to achieve the required pump speed n.

[0048] Step S4, the intelligent remote control system 12 monitors the flow on the corresponding pipeline through the cooling water pipeline flow meter 10 and the chilled water pipeline flow meter 9.

[0049] Step S5, if the frequency-regulated flow meets the refrigeration demand, the terminal demand is met; otherwise, step S3 is repeated for frequency regulation until the flow demand is met.

[0050] Terminal demand: the appropriate refrigeration capacity corresponding to the central air conditioning terminal load rate, which avoids excessive refrigeration capacity and excessive energy loss.

[0051] Flow demand: the chilled water flow size corresponding to the required refrigeration capacity of the central air conditioning terminal, which determines the cooling water flow size during heat exchange of the refrigeration unit, so that the flow is controlled by pump frequency regulation to meet the flow demand.

[0052] In some embodiments of the present application, step S3 includes: the cooling water pump 2 and the chilled water pump 6 match the required pump frequency f through the pump characteristic curve of the cooling water pump and the chilled water pump, combined with the required flow of cooling water and chilled water calculated in step S2; the pump speed n is adjusted through the frequency converter to meet the cooling water and chilled water flow demand.

[0053] Specifically, step S3 includes: the intelligent remote control system 12 calculates the cooling water and chilled water flow demand signal F1 output according to the refrigeration capacity demand of the central air conditioning terminal, and subtracts the existing cooling water and chilled water flow signal F2 (the existing cooling water and chilled water flow signal F2 is the monitoring result of the flow meter on the corresponding cooling water and chilled water pipeline uploaded to the intelligent remote control system) to obtain a difference ΔF; the pump characteristic curve of the cooling water pump 2 and the chilled water pump 6 is matched, wherein the pump characteristic curve includes the relationship curves of head H and flow F, efficiency η and flow F, and shaft power P and flow F, combined with the flow demand, to calculate and match the low-power high-efficiency point (at which both low power and high efficiency are achieved) and the required pump frequency f; the pump speed n is adjusted through the frequency converter.

[0054] In the water pump characteristic curve, there are the relationship curves of head H and flow F, efficiency η and flow F, shaft power P and flow F, etc., according to the flow signal F1 and ΔF (ΔF represents a flow adjustment process from F1 to F2, that is, there is a difference signal between F1 and F2, and through matching the characteristic curve, it is adjusted to the corresponding F1), according to the relationship curves of efficiency and shaft power and flow, the low-power and high-efficiency point with better effect is obtained, and the water pump frequency corresponding to the point is the required water pump frequency f. The entire control system achieves energy saving and high efficiency.

[0055] In some embodiments of the application, in steps S4-S5, whether the flow F after frequency adjustment meets the cooling water and chilled water flow demand signal F1 is judged through flow meter monitoring, if not equal, then the low-power and high-efficiency point is matched again through the water pump characteristic curve, so as to meet the cooling water and chilled water flow demand signal F1, satisfy the refrigeration demand of the central air conditioning terminal 7, and achieve the refrigeration demand, otherwise, it is ended.

[0056] The system and method provided by the foregoing embodiments of the application associate the variable frequency water pump, the intelligent remote control system and the load rate of the central air conditioning terminal, can obtain the required flow through the intelligent remote control system according to the actual demand, adjust the rotating speed of the water pump, match the operating characteristic curve of the water pump with the flow demand in the system, thereby effectively avoid the unnecessary loss of energy, adjust the voltage while frequency conversion, thereby reduce the power consumption of the water pump, and when the water pump is stopped, the air pump can be used to empty the residual water in the centrifugal pump, avoid the residual water causing corrosion, corrosion and microbial breeding, affect the performance and service life of the centrifugal pump, realize significant energy saving effect, improve the overall operation efficiency, and strive for the overall optimization of the central air conditioning refrigeration machine room, optimize the key links such as the water pump, and aim to reduce the building energy consumption and improve the system energy efficiency.

[0057] The embodiments of the application are described in detail above in combination with the drawings, but the application is not limited to the above embodiments, and various changes can be made within the knowledge range of ordinary skilled persons in the art without departing from the purpose of the application.

Claims

1. A refrigeration plant room energy saving control system based on water pump frequency modulation, characterized in that, The system comprises a cooling tower (1), a cooling water pump (2), a refrigeration unit (4), a chilled water pump (6), a central air conditioning terminal (7) and an intelligent remote control system (12), The cooling tower (1) is connected with the refrigeration unit (4) through a cooling water pipeline, and the cooling water pump (2) is connected with the cooling water pipeline. The refrigeration unit (4) is connected with the central air conditioning terminal (7) through a chilled water pipeline, the chilled water pump (6) is connected with the chilled water pipeline, and the cooling water pipeline and the chilled water pipeline are respectively provided with a cooling water pipeline flowmeter (10) and a chilled water pipeline flowmeter (9). The chilled water pipeline flowmeter (9), the cooling water pipeline flowmeter (10), the cooling water pump (2), the chilled water pump (6) and the central air conditioning terminal (7) are connected with the intelligent remote control system (12). The intelligent remote control system (12) is used for calculating the required flow of cooling water and chilled water according to the load rate of the central air conditioning terminal (7), and the cooling water pump (2) and the chilled water pump (6) match a low-power high-efficiency point in the pump characteristic curve by combining the required flow of cooling water and chilled water, and the pump frequency corresponding to the low-power high-efficiency point is the required pump frequency, The system further comprises a cooling water gas pump (21) and a chilled water gas pump (22), which are connected to the water inlets of the cooling water pump and the chilled water pump through hoses respectively, the cooling water gas pump (21) is connected to the water inlet of the cooling water pump (2) through a hose, the chilled water gas pump (22) is connected to the water inlet of the chilled water pump (6) through a hose, and compressed air is introduced to exhaust the residual liquid in the pump when the system is stopped.

2. The energy-saving control system for refrigeration plant room based on frequency modulation of water pump according to claim 1, characterized in that, The cooling water pipeline comprises a cooling water supply pipeline (3) and a cooling water outlet pipeline (11), the cooling tower (1) and the refrigeration unit (4) are connected to form a loop through the cooling water supply pipeline (3) and the cooling water outlet pipeline (11), the cooling water pump (2) is connected with the cooling water supply pipeline (3), and the cooling water pipeline flowmeter (10) is arranged on the cooling water supply pipeline (3).

3. The energy-saving control system for refrigeration plant rooms based on frequency modulation of water pumps according to claim 1, characterized in that, The chilled water pipeline comprises a chilled water supply pipeline (5) and a chilled water outlet pipeline (8), the refrigeration unit (4) and the central air conditioning terminal (7) are connected to form a loop through the chilled water supply pipeline (5) and the chilled water outlet pipeline (8), the chilled water pump (6) is connected with the chilled water supply pipeline (5), and the chilled water pipeline flowmeter (9) is arranged on the chilled water supply pipeline (5).

4. A method for energy saving control of a refrigeration plant room based on frequency modulation of a water pump, characterized in that, The system is realized based on any one of claims 1-3, and the method comprises the following steps: Step S1, the intelligent remote control system (12) monitors the load rate of the central air conditioning terminal (7); Step S2, the intelligent remote control system (12) calculates the required flow of cooling water and chilled water according to the load rate, and outputs a cooling water and chilled water flow demand signal F1 to the cooling water pump (2) and the chilled water pump (6); Step S3, the cooling water pump (2) and the chilled water pump (6) are frequency-adjusted according to the flow demand to reach the required rotating speed n. Step S4, the intelligent remote control system (12) monitors the flow in the corresponding pipeline through the chilled water pipeline flow meter (10) and the chilled water pipeline flow meter (9); Step S5, if the frequency-adjusted flow meets the refrigeration demand, the terminal demand is met; otherwise, step S3 is repeated to adjust the frequency until the flow demand is met, achieving energy-saving effect.

5. The energy-saving control method for refrigeration plant rooms based on frequency modulation of water pumps according to claim 4, characterized in that, In step S3, the chilled water pump (2) and the chilled water pump (6) match the water pump frequency of the chilled water pump (2) and the chilled water pump (6) in the water pump characteristic curve of the chilled water pump and the chilled water pump, respectively, based on the required flow of the chilled water and the chilled water in step S2, and adjust the speed of the corresponding water pump based on the water pump frequency.

6. The energy-saving control method for refrigeration plant rooms based on frequency modulation of water pumps according to claim 5, characterized in that, When matching the water pump frequency, the difference ΔF is obtained by subtracting the existing chilled water and chilled water flow signals F2 from the chilled water and chilled water flow demand signals F1. According to the chilled water and chilled water flow demand signals F1 and the difference ΔF, and combining the efficiency, shaft power and flow relationship curve in the water pump characteristic curve, the low-power high-efficiency point is matched to obtain the required water pump frequency f.

7. The energy-saving control method for refrigeration plant rooms based on frequency modulation of water pumps according to claim 5, characterized in that, In steps S4-S5, the flow obtained after frequency adjustment is monitored through the chilled water pipeline flow meter (10) and the chilled water pipeline flow meter (9), and it is judged whether the flow after frequency adjustment is equal to the chilled water and chilled water flow demand signal F1. If not, the low-power high-efficiency point is matched again through the water pump characteristic curve to achieve the chilled water and chilled water flow demand signal F1, meet the refrigeration demand of the central air conditioning terminal (7), and achieve the refrigeration demand; otherwise, it is ended.

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