A fluorine refrigeration system, double cold source air conditioning unit and control method

Abstract

The application discloses a fluorine refrigeration system, a double-cold-source air conditioning unit and a control method, belongs to the technical field of computer room air conditioning, and the fluorine refrigeration system comprises a compressor, an evaporator and a condenser. The compressor, the evaporator and the condenser are connected to form a refrigerant circulation loop. The number of the evaporators is at least two, and the evaporators are arranged in parallel. An expansion valve group is connected in series on the circulation loop between the evaporator and the condenser, and the expansion valve group comprises at least two parallel electronic expansion valves. The electronic expansion valve group with a small flow aperture solves the problem of sudden change of superheat when the evaporator switches between high-load and low-load working conditions on the basis of guaranteeing the operation requirements of the evaporator under low-load and high-load working conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of machine room air conditioning, in particular to a fluorine refrigeration system, a double cold source air conditioning unit and a control method. BACKGROUND

[0002] The fluorine system is a common type of air conditioning system, which uses refrigerant (usually freon or other types of refrigerant) as a medium for transferring cold or heat.

[0003] In the process of implementing the present application, the inventors found that the prior art at least has the following problems:

[0004] The evaporator in the existing fluorine system is usually connected in series with only one expansion valve, and the pressure and flow of the refrigerant entering the evaporator are adjusted by the opening degree of the expansion valve; in order to meet the high evaporation pressure requirement of the evaporator in high load operation, a large flow aperture expansion valve is usually selected, but when the evaporator switches between high load and low load, due to the large flow aperture of the expansion valve, the flow range adjusted by the large flow aperture expansion valve is larger under the same opening degree change, thus causing the superheat to suddenly increase, resulting in hot spots in the air outlet and affecting the stable operation of the fluorine system.

[0005] Therefore, in view of the above technical problems, how to make the expansion valve meet the operating requirements of the evaporator in high load and low load operation, and avoid sudden changes in superheat when the evaporator switches between high load and low load is a technical problem that needs to be solved by those skilled in the art. SUMMARY

[0006] The purpose of the present application is to provide a fluorine refrigeration system, a double cold source air conditioning unit and a control method, which solves the problem of sudden change in superheat when the evaporator switches between high load and low load, while ensuring the operating requirements of the evaporator in low load and high load operation, by using a small flow aperture electronic expansion valve group.

[0007] To achieve the above-mentioned purpose, the present application provides a fluorine refrigeration system, comprising a compressor, an evaporator and a condenser, the compressor, the evaporator and the condenser are connected to form a circulation loop of refrigerant, the number of evaporators is at least two, and the evaporators are connected in parallel, and an expansion valve group is connected in series on the circulation loop between the evaporator and the condenser, the expansion valve group comprises at least two parallel electronic expansion valves.

[0008] Preferably, the expansion valve group is connected in series on the parallel branch corresponding to each evaporator, and the expansion valve groups connected in series by different evaporators are connected in parallel.

[0009] Preferably, in any one of the groups of the expansion valve groups, the expansion valve group comprises a first electronic expansion valve and a second electronic expansion valve connected in parallel, the first electronic expansion valve and the second electronic expansion valve have the same specifications, and the paths of the refrigerant flowing from the first electronic expansion valve and the second electronic expansion valve to the corresponding evaporators have the same length.

[0010] Preferably, the expansion valve group comprises a third electronic expansion valve, a fourth electronic expansion valve, and a fifth electronic expansion valve, the third electronic expansion valve is connected in series on one parallel branch of the evaporators, the fourth electronic expansion valve is connected in series on another parallel branch of the evaporators, and the fifth electronic expansion valve is connected in parallel with the third electronic expansion valve and the fourth electronic expansion valve.

[0011] Preferably, the third electronic expansion valve and the fourth electronic expansion valve have the same specifications, and the flow rate of the fifth electronic expansion valve is greater than that of the third electronic expansion valve or the fourth electronic expansion valve at the same opening degree.

[0012] Preferably, the first end of the fifth electronic expansion valve is connected to the first end of the third electronic expansion valve and the first end of the fourth electronic expansion valve, respectively, and the second end of the fifth electronic expansion valve is connected to the second end of the third electronic expansion valve and the second end of the fourth electronic expansion valve through a first one-way valve and a second one-way valve, respectively.

[0013] Preferably, the first end of the third electronic expansion valve, the fourth electronic expansion valve, and the fifth electronic expansion valve is connected to the condenser, the flow direction of the first one-way valve is from the second end of the fifth electronic expansion valve to the branch where the third electronic expansion valve is located, and the flow direction of the second one-way valve is from the second end of the fifth electronic expansion valve to the branch where the fourth electronic expansion valve is located.

[0014] A dual-cold-source air conditioning unit, comprising:

[0015] A chilled water system comprising a chilled water circulation loop, a chilled water coil, and a cooling unit arranged on the chilled water circulation loop.

[0016] A fluorine refrigeration system, which is the fluorine refrigeration system described above.

[0017] Preferably, the evaporator of the fluorine refrigeration system is an evaporating coil, the evaporating coil corresponds in position to the chilled water coil, and a plurality of evaporating coils and the chilled water coil are arranged in series in the airflow direction.

[0018] A control method applied to the dual-cold-source air conditioning unit described above, the control method comprising:

[0019] According to the cold quantity demand of the machine room, the chilled water system or / and the fluorine refrigeration system is operated;

[0020] When the fluorine refrigeration system is operated, the first evaporation pressure of the corresponding evaporator when one of the electronic expansion valves in the expansion valve group is in low pressure ratio full load is obtained;

[0021] The current second evaporation pressure of the evaporator is detected by the pressure sensor, if the second evaporation pressure is less than the first evaporation pressure, only one of the electronic expansion valves is opened, and the opening degree of the electronic expansion valve is adjusted according to the second evaporation pressure, if the second evaporation pressure is greater than or equal to the first evaporation pressure, the other electronic expansion valve is opened, and the two electronic expansion valves simultaneously provide refrigerant for the corresponding evaporator.

[0022] Preferably, when the fluorine refrigeration system is operated, the first electronic expansion valve is automatically opened, the first evaporation pressure of the corresponding evaporator when the first electronic expansion valve is in low pressure ratio full load is detected, and whether to open the second electronic expansion valve is determined according to the size relationship between the first evaporation pressure and the second evaporation pressure.

[0023] Preferably, when the fluorine refrigeration system is operated, the third electronic expansion valve and the fourth electronic expansion valve are automatically opened, the first evaporation pressure of the corresponding evaporator when the third electronic expansion valve or the fourth electronic expansion valve is in low pressure ratio full load is detected, and whether to open the fifth electronic expansion valve is determined according to the size relationship between the first evaporation pressure and the second evaporation pressure.

[0024] Compared with the prior art, the technical scheme provided by the application has at least the following beneficial effects:

[0025] The application replaces the traditional large-flow aperture expansion valve with the expansion valve group, and the expansion valve group adopts at least two parallel electronic expansion valves, so that the flow aperture of the parallel electronic expansion valves is obviously smaller on the basis that the maximum flow of the fluorine refrigeration system is constant. When the evaporator is in low load, only one electronic expansion valve can be opened to ensure the normal opening degree of the electronic expansion valve, and when the opened electronic expansion valve is in low pressure ratio full load, another electronic expansion valve connected in parallel can be opened, so that the normal opening degree of the small valve in low load can be realized, and the operation demand in high load can be met. At the same time, the application adopts the parallel small-flow aperture electronic expansion valve, so that when the opening degree of the small-flow aperture electronic expansion valve changes during the switching of the high and low loads of the evaporator, the influence on the superheat degree of the system is smaller, the sudden change of the superheat degree is avoided, and the operation stability of the fluorine refrigeration system is improved. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only constitute a part of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on the provided drawings.

[0027] Figure 1 The first expansion valve group setting structure schematic diagram of the fluorine refrigeration system provided by the embodiments of the present application is shown in the figure.

[0028] Figure 2 The second expansion valve group setting structure schematic diagram of the fluorine refrigeration system provided by the embodiments of the present application is shown in the figure.

[0029] In the figure: 1-compressor; 2-evaporator; 3-condenser; 4-circulation loop; 5-expansion valve group; 51-first electronic expansion valve; 52-second electronic expansion valve; 53-third electronic expansion valve; 54-fourth electronic expansion valve; 55-fifth electronic expansion valve; 6-chilled water coil; 7-cooling unit; 8-chilled water circulation loop. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments only constitute a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] It should be noted that in the present embodiment, the directions or position relationships indicated by "up", "down", "front", "back" and the like are based on the directions or position relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and thus cannot be understood as indicating or implying that the devices or elements must have a particular direction, be constructed and operated in a particular direction, and thus cannot be understood as limiting the present application. In addition, "first", "second", "third", "fourth" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0032] In order to make the skilled in the art better understand the present application, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0033] Please refer to Figure 1 and Figure 2In the embodiment, a fluorine refrigeration system is provided, which comprises a compressor 1, an evaporator 2 and a condenser 3, and the compressor 1, the evaporator 2 and the condenser 3 are connected to form a circulation loop 4 of fluorine refrigerant. In the embodiment, the number of evaporators 2 in the fluorine refrigeration system is at least two, and the evaporators 2 are arranged in parallel, so that when one of the evaporators 2 fails or needs maintenance, the other evaporator 2 connected in parallel can still work normally, thereby ensuring the cooling capacity of the machine room and avoiding the temperature rise of the machine room.

[0034] On the basis of the parallel arrangement of the evaporators 2, an expansion valve group 5 is connected in series between the evaporator 2 and the condenser 3, specifically, the expansion valve group 5 can be connected in series on each parallel branch of the evaporator 2, and at this time, the number of the expansion valve group 5 is consistent with that of the evaporator 2; please refer to Figure 1 The expansion valve groups 5 connected in series with different evaporators 2 are arranged in parallel, and each expansion valve seat can adjust the flow of fluorine refrigerant on the corresponding parallel branch.

[0035] Further, in any one expansion valve group 5, the expansion valve group 5 comprises a first electronic expansion valve 51 and a second electronic expansion valve 52 connected in parallel. Considering that one of the first electronic expansion valve 51 and the second electronic expansion valve 52 can be opened when the evaporator 2 is in low load, thereby meeting the low load demand of the evaporator 2, the first electronic expansion valve 51 and the second electronic expansion valve 52 can be set as electronic expansion valves with the same specifications, so as to ensure that the flow control of the fluorine refrigerant is the same when the first electronic expansion valve 51 or the second electronic expansion valve 52 is opened under the condition that the opening degree changes, that is, the flow control of the refrigerant remains consistent in the two cases of opening the first electronic expansion valve 51 or the second electronic expansion valve 52 alone, thereby ensuring the control stability of the fluorine refrigeration system.

[0036] The specifications of the first electronic expansion valve 51 and the second electronic expansion valve 52 include flow aperture, control accuracy, working pressure, etc.

[0037] In addition, in order to further ensure that the flow control of the first electronic expansion valve 51 and the second electronic expansion valve 52 remains consistent, the path length of the fluorine refrigerant flowing from the first electronic expansion valve 51 and the second electronic expansion valve 52 to the corresponding evaporator 2 is the same, thereby avoiding the case that the refrigerant resistance is different due to different path lengths, and the different refrigerant resistance also causes a certain deviation in the flow control of the first electronic expansion valve 51 and the second electronic expansion valve 52.

[0038] As mentioned above, the first or second electronic expansion valve 52 can be opened only when the evaporator 2 is in low load, but when the low pressure ratio of the opened electronic expansion valve is full load, another electronic expansion valve in parallel therewith can be opened, so that the normal opening of the small valve in low load can be realized, and the operation demand in high load can be met. Meanwhile, the expansion valve group 5 can control the refrigerant amount of the corresponding evaporator 2 independently, and does not affect each other, so that the accurate adjustment of each expansion valve group 5 can be realized according to the evaporation pressure of each evaporator 2.

[0039] In another embodiment, the expansion valve group 5 is connected in series on the circulating loop 4 between the evaporator 2 and the condenser 3, and further comprises that the expansion valve group 5 is connected in series in two parallel branches at the same time, please refer to Figure 2 The expansion valve group 5 of this embodiment comprises a third electronic expansion valve 53, a fourth electronic expansion valve 54 and a fifth electronic expansion valve 55; specifically, the third electronic expansion valve 53 is connected in series on the parallel branch of one evaporator 2, the fourth electronic expansion valve 54 is connected in series on the parallel branch of another evaporator 2, and the fifth electronic expansion valve 55 is connected in parallel with the third electronic expansion valve 53 and the fourth electronic expansion valve 54 at the same time.

[0040] The fifth electronic expansion valve 55 can be used as a backup valve of the third electronic expansion valve 53 and the fourth electronic expansion valve 54 at the same time, when the two evaporators 2 are in low load operation, the third electronic expansion valve 53 and the fourth electronic expansion valve 54 can be opened only, and the normal opening of the two electronic expansion valves can be maintained, at this time, the opening of the electronic expansion valve on the corresponding parallel branch can be automatically adjusted according to the evaporation pressure of the evaporator 2; when the third electronic expansion valve 53 and the fourth electronic expansion valve 54 are in full load in low pressure ratio, the fifth electronic expansion valve 55 can be opened, and the fifth electronic expansion valve 55 can supplement fluorine refrigerant for the two evaporators 2 at the same time, so as to adapt to the high load operation demand of the evaporator 2.

[0041] It should be pointed out that since the fifth electronic expansion valve 55 can supplement fluorine refrigerant for the two evaporators 2 at the same time after being opened, the evaporation pressures of the two evaporators 2 should be roughly equivalent, so that after the fluorine refrigerant is supplemented, the two evaporators 2 can meet the high load operation. On this basis, the third electronic expansion valve 53 and the fourth electronic expansion valve 54 should also be kept the same specification, so as to ensure that when the evaporation pressures of the two evaporators 2 are roughly equivalent, the fifth electronic expansion valve 55 as a backup valve can provide roughly equivalent fluorine refrigerant amount for the two evaporators 2.

[0042] Meanwhile, the expansion valve group 5 adopts at least two parallel electronic expansion valves, and the flow aperture of the parallel electronic expansion valves is obviously smaller on the basis that the maximum flow of the fluorine refrigeration system is constant, so that the electronic expansion valve can provide more accurate flow control. On this basis, the flow aperture of the third electronic expansion valve 53 and the fourth electronic expansion valve 54 is smaller, and in order to meet the maximum flow of the fluorine refrigeration system, the flow aperture of the fifth electronic expansion valve 55 should also be large enough, so as to provide sufficient refrigerant supplement for the two evaporators 2. In some embodiments, the flow of the fifth electronic expansion valve 55 is greater than that of the third electronic expansion valve 53 or the fourth electronic expansion valve 54 under the same opening degree, so as to ensure that sufficient refrigerant supplement can be provided for the two evaporators 2.

[0043] Please refer to Figure 2 The first end of the fifth electronic expansion valve 55 is connected with the first end of the third electronic expansion valve 53 and the first end of the fourth electronic expansion valve 54 respectively, and the second end of the fifth electronic expansion valve 55 is connected with the second end of the third electronic expansion valve 53 and the second end of the fourth electronic expansion valve 54 through the first one-way valve and the second one-way valve respectively. The first end of the third electronic expansion valve 53, the fourth electronic expansion valve 54 and the fifth electronic expansion valve 55 is connected with the condenser 3. The flow direction of the first one-way valve is the direction from the second end of the fifth electronic expansion valve 55 to the branch where the third electronic expansion valve 53 is located, and the flow direction of the second one-way valve is the direction from the second end of the fifth electronic expansion valve 55 to the branch where the fourth electronic expansion valve 54 is located. By arranging the first one-way valve and the second one-way valve, the refrigerant in the corresponding parallel branches of the two evaporators 2 can be prevented from flowing into each other, so as to ensure the stable operation of the two evaporators 2.

[0044] In summary of the above embodiments, the expansion valve group 5 of the present application replaces the traditional large-flow-aperture expansion valve, and the expansion valve group 5 adopts at least two parallel electronic expansion valves, and the flow aperture of the parallel electronic expansion valves is obviously smaller on the basis that the maximum flow of the fluorine refrigeration system is constant. When the evaporator 2 is in low load, only one electronic expansion valve can be opened to ensure the normal opening degree of the electronic expansion valve, and when the opening electronic expansion valve is in low pressure ratio compared with full load, another electronic expansion valve in parallel with it can be opened, so that the normal opening degree of the small valve in low load can be realized, and the operation demand in high load can also be met. Meanwhile, the present application adopts parallel small-flow-aperture electronic expansion valves, so that when the opening degree of the small-flow-aperture electronic expansion valve changes during the switching of the high and low loads of the evaporator 2, the influence on the system superheat is smaller, the sudden change of the superheat is avoided, and the operation stability of the fluorine refrigeration system is improved.

[0045] The present application also provides a double-cold-source air conditioning unit, please refer to Figure 1 or Figure 2The air conditioning unit comprises a chilled water system and a fluorine refrigeration system, the chilled water system comprises a chilled water circulation loop 8, a chilled water coil 6 and a cooling unit 7 arranged on the chilled water circulation loop 8, and the fluorine refrigeration system is the fluorine refrigeration system described above. The evaporator 2 of the fluorine refrigeration system is an evaporating coil, and the evaporating coil corresponds to the position of the chilled water coil 6, so that a plurality of evaporating coils can be arranged in series in the airflow direction with the chilled water coil 6, that is, in series ventilation. The series in the airflow direction means that the air return flow of the machine room can flow through the evaporating coil and the chilled water coil 6 in turn, or flow through the chilled water coil 6 and the evaporating coil in turn, so that the chilled water system or the fluorine refrigeration system can be operated alone according to the actual cooling capacity demand of the machine room, and the two systems can also be operated simultaneously.

[0046] Since the dual cold source air conditioning unit comprises a fluorine refrigeration system, the dual cold source air conditioning unit also has the beneficial effects of the expansion valve group 5 in the fluorine refrigeration system.

[0047] The application also provides a control method, which can be applied to the dual cold source air conditioning unit described above, and the control method comprises the following steps:

[0048] According to the cooling capacity demand of the machine room, the chilled water system or / and the fluorine refrigeration system is operated;

[0049] When the fluorine refrigeration system is operated, the first evaporation pressure of the corresponding evaporator 2 at low pressure ratio full load of one of the electronic expansion valves of the expansion valve group 5 can be obtained through the corresponding pressure sensor;

[0050] Meanwhile, when the fluorine refrigeration system is operated, the evaporation pressure of the evaporator 2 will change according to the cooling capacity demand of the machine room, so the opening degree of the corresponding electronic expansion valve will also change. On this basis, the second evaporation pressure of the evaporator 2 can be detected by the pressure sensor. If the second evaporation pressure is less than the first evaporation pressure, it means that one electronic expansion valve can meet the current load requirement of the evaporator 2, so only one electronic expansion valve needs to be opened, and the opening degree of the electronic expansion valve can be adjusted according to the second evaporation pressure. If the second evaporation pressure is greater than or equal to the first evaporation pressure, it means that the electronic expansion valve that has been opened cannot meet the high load operation demand of the evaporator 2, so another electronic expansion valve in parallel needs to be opened to supplement sufficient fluorine refrigerant for the evaporator 2 to meet the high load operation demand of the evaporator 2.

[0051] The small flow aperture electronic expansion valve in parallel is adopted, and when the opening degree of the small flow aperture electronic expansion valve changes during the high and low load switching of the evaporator 2, the influence on the system superheat degree is smaller, and the sudden change of the superheat degree is avoided.

[0052] In the first embodiment, the expansion valve group 5 includes a first electronic expansion valve 51 and a second electronic expansion valve 52. When the fluorine refrigeration mode is operated, the first electronic expansion valve 51 is automatically opened, and the opening degree of the first electronic expansion valve 51 is automatically adjusted according to the evaporation pressure of the evaporator 2. According to the above control method, the first evaporation pressure of the corresponding evaporator 2 when the first electronic expansion valve 51 is in a low pressure ratio full load state needs to be detected, and whether the second electronic expansion valve 52 is opened is determined according to the size relationship between the first evaporation pressure and the second evaporation pressure. Specifically, when the second evaporation pressure is less than the first evaporation pressure, the evaporator 2 is in a low load state, and therefore the first electronic expansion valve 51 can be continuously opened. When the second evaporation pressure is greater than or equal to the first evaporation pressure, it indicates that the first electronic expansion valve 51 is in a low pressure ratio full load state, and therefore the second electronic expansion valve 52 needs to be opened, so that the two electronic expansion valves simultaneously provide refrigerant for the corresponding evaporator 2. In this way, the normal opening degree of the first electronic expansion valve 51 when the evaporator 2 is in a low load state can be realized, and the operating requirements of the evaporator 2 in a high load state can be met.

[0053] Of course, when the fluorine refrigeration mode is operated, the second electronic expansion valve 52 can also be automatically opened. The second electronic expansion valve 52 and the first electronic expansion valve 51 can be equivalent to replace each other. The subsequent steps of opening the second electronic expansion valve 52 are described above and will not be repeated here.

[0054] In the second embodiment, the expansion valve group 5 includes a third electronic expansion valve 53, a fourth electronic expansion valve 54, and a fifth electronic expansion valve 55. When the fluorine refrigeration system is operated, the third electronic expansion valve 53 and the fourth electronic expansion valve 54 are automatically opened to meet the normal operation of the two evaporators 2, and to ensure the normal opening degree of the third electronic expansion valve 53 and the fourth electronic expansion valve 54. According to the above control method, the first evaporation pressure of the corresponding evaporator 2 when the third electronic expansion valve 53 or the fourth electronic expansion valve 54 is in a low pressure ratio full load state needs to be detected, and whether the fifth electronic expansion valve 55 is opened is determined according to the size relationship between the first evaporation pressure and the second evaporation pressure. Specifically, when the second evaporation pressure is less than the first evaporation pressure, the evaporator 2 is in a low load state, and therefore the third electronic expansion valve 53 and the fourth electronic expansion valve 54 can be continuously opened. When the second evaporation pressure is greater than or equal to the first evaporation pressure, it indicates that the third electronic expansion valve 53 or the fourth electronic expansion valve 54 is in a low pressure ratio full load state, and therefore the fifth electronic expansion valve 55 needs to be opened, so that the fifth electronic expansion valve 55 simultaneously provides refrigerant for the two evaporators 2 to meet the operating requirements in a high load state.

[0055] In summary, the control method can meet the operation requirements of the evaporator 2 in the low-load working condition and the high-load working condition, and can control the opening degree of the corresponding electronic expansion valve and control the opening and closing of different electronic expansion valves according to the evaporation pressure of the evaporator 2, so as to reduce the influence on the system superheat degree through the electronic expansion valve with a small flow aperture, and improve the operation stability of the fluorine refrigeration system.

[0056] It should be noted that the relational terms herein, such as first and second, are used only to distinguish one entity from another, and do not necessarily require or imply any actual relationship or order between or among the entities.

[0057] The principles and implementation modes of the present application are described by applying specific examples herein, and the above examples are only used to help understand the method and core idea of the present application. It should be pointed out that, for ordinary skilled in the art, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A fluorine refrigeration system characterized by comprising: The air conditioner comprises a compressor (1), an evaporator (2) and a condenser (3), the compressor (1), the evaporator (2) and the condenser (3) are connected to form a refrigerant circulation loop (4), the number of the evaporator (2) is at least two, and the evaporator (2) is arranged in parallel, and an expansion valve group (5) is arranged in series on the circulation loop (4) between the evaporator (2) and the condenser (3), and the expansion valve group (5) comprises at least two parallel electronic expansion valves; The expansion valve group (5) comprises a third electronic expansion valve (53), a fourth electronic expansion valve (54) and a fifth electronic expansion valve (55), the third electronic expansion valve (53) is arranged in series on a parallel branch of one of the evaporators (2), the fourth electronic expansion valve (54) is arranged in series on a parallel branch of another of the evaporators (2), and the fifth electronic expansion valve (55) is connected in parallel with the third electronic expansion valve (53) and the fourth electronic expansion valve (54). The third electronic expansion valve (53) and the fourth electronic expansion valve (54) have the same specification, and the flow rate of the fifth electronic expansion valve (55) is greater than that of the third electronic expansion valve (53) or the fourth electronic expansion valve (54) at the same opening degree.

2. The fluorinated refrigeration system of claim 1, wherein, The first end of the fifth electronic expansion valve (55) is connected with the first end of the third electronic expansion valve (53) and the first end of the fourth electronic expansion valve (54) respectively, and the second end of the fifth electronic expansion valve (55) is connected with the second end of the third electronic expansion valve (53) and the second end of the fourth electronic expansion valve (54) through a first one-way valve and a second one-way valve respectively. The first end of the third electronic expansion valve (53), the fourth electronic expansion valve (54) and the fifth electronic expansion valve (55) is connected with the condenser (3), the flow direction of the first one-way valve is the direction from the second end of the fifth electronic expansion valve (55) to the branch where the third electronic expansion valve (53) is arranged, and the flow direction of the second one-way valve is the direction from the second end of the fifth electronic expansion valve (55) to the branch where the fourth electronic expansion valve (54) is arranged.

3. A dual cold source air conditioning unit, characterized by, It comprises: A chilled water system comprising a chilled water circulation loop (8) and a chilled water coil (6) and a cooling unit (7) arranged on the chilled water circulation loop (8); The fluorine refrigeration system is the fluorine refrigeration system according to any one of claims 1-2; The evaporator (2) of the fluorine refrigeration system is an evaporating coil, the evaporating coil corresponds to the position of the chilled water coil (6), and a plurality of evaporating coils and the chilled water coil (6) are arranged in series in the air flow direction.

4. A control method characterized by, The control method is applied to the double-cold-source air conditioning unit of claim 3, and the control method comprises: According to the cooling capacity demand of the machine room, the chilled water system or / and the fluorine refrigeration system is operated; When the fluorine refrigeration system is operated, the first evaporation pressure of the corresponding evaporator (2) of one of the electronic expansion valves of the expansion valve group (5) at low pressure ratio full load is obtained; The current second evaporation pressure of the evaporator (2) is detected by a pressure sensor, if the second evaporation pressure is less than the first evaporation pressure, only one electronic expansion valve is opened, and the opening of the electronic expansion valve is adjusted according to the second evaporation pressure; if the second evaporation pressure is greater than or equal to the first evaporation pressure, another electronic expansion valve is opened, and the two electronic expansion valves simultaneously provide refrigerant for the corresponding evaporator (2).

5. The control method according to claim 4, characterized by When the fluorine refrigeration system is running, the first electronic expansion valve (51) is automatically opened, the first evaporation pressure of the corresponding evaporator (2) when the first electronic expansion valve (51) is in low pressure ratio full load is detected, and whether to open the second electronic expansion valve (52) is judged according to the size relationship between the first evaporation pressure and the second evaporation pressure.

6. The control method according to claim 4, characterized by When the fluorine refrigeration system is running, the third electronic expansion valve (53) and the fourth electronic expansion valve (54) are automatically opened, the first evaporation pressure of the corresponding evaporator (2) when the third electronic expansion valve (53) or the fourth electronic expansion valve (54) is in low pressure ratio full load is detected, and whether to open the fifth electronic expansion valve (55) is judged according to the size relationship between the first evaporation pressure and the second evaporation pressure.

Images