Energy storage structure, air conditioning system, and control method

Abstract

The present application provides an energy storage structure, an air conditioning system, and a control method. The energy storage structure comprises: a heat exchanger; an energy accumulator; a refrigerant inlet pipe, one end of the refrigerant inlet pipe being connected to the energy accumulator and the other end of the refrigerant inlet pipe being connected to the heat exchanger, so as to introduce a refrigerant into the energy accumulator; a refrigerant outlet pipe, one end of the refrigerant outlet pipe being connected to the energy accumulator and the other end of the refrigerant outlet pipe being connected to the heat exchanger, so as to convey the refrigerant from the energy accumulator into the heat exchanger; an expansion valve, disposed on the refrigerant inlet pipe to control the flow rate of the refrigerant inlet pipe; a pressure sensor, disposed on a compressor suction pipe; an outlet pipe temperature sensor, disposed on the refrigerant outlet pipe; and a control module, the control model being in signal connection with the expansion valve, the pressure sensor, and the outlet pipe temperature sensor, so as to control the degree of opening of the expansion valve on the basis of signals from the pressure sensor and the outlet pipe temperature sensor. The energy storage structure of the present application solves the technical problem in the prior art of low heat exchange efficiency in cold storage devices.

Description

Energy storage structure, air conditioning system and control method

[0001] This application claims priority to the patent application filed with the State Intellectual Property Office of China on December 11, 2023, with application number 202311685760.6 and application name “A storage structure, air conditioning system and control method”. Technical Field

[0002] The present application relates to the field of multi-split systems, and specifically to an energy storage structure, an air conditioning system, and a control method. Background Art

[0003] An ice storage device integrated into a VRF unit uses the outdoor heat exchanger as the condenser and the ice storage device as the evaporator. This cools the water within and freezes it, storing the cold in the ice storage device. During this process, the refrigerant evaporates and exchanges heat with the water, similar to the air-cooled evaporation of refrigerant in conventional indoor units, but with the following differences: First, the heat transfer characteristics of water differ from those of air: a different heat transfer coefficient, a wider temperature range, and phase changes in the water. Second, while air-cooled indoor units can adjust heat exchange by adjusting air volume, the water in an ice storage device remains stationary, preventing adjustments to its flow and thus affecting heat exchange. Third, the refrigerant heat exchange tubes have longer flow paths and larger diameters, resulting in greater thermal inertia and pressure loss. Fourth, the temperature detected by the temperature sensor in the water / ice is not stable, but rather fluctuates significantly.

[0004] The above four differences result in the refrigerant evaporation heat exchange in the ice storage device cannot be adjusted like the evaporation process in a conventional air-cooled indoor unit. The existing settings cannot formulate a suitable control method based on the heat exchange laws between the refrigerant and water and ice to achieve efficient cold storage, resulting in low heat exchange efficiency of the cold storage device.

[0005] Therefore, the prior art needs to be further developed.

[0006] Summary of the Invention

[0007] The purpose of this application is to overcome the above technical deficiencies and provide an energy storage structure, an air conditioning system and a control method to solve the technical problem of low heat exchange efficiency of cold storage devices in the prior art.

[0008] In order to achieve the above-mentioned technical objectives, the present application adopts the following technical solutions: an energy storage structure is provided, including: a heat exchanger; an accumulator; a refrigerant inlet pipe, one end of the refrigerant inlet pipe is connected to the accumulator, and the other end of the refrigerant inlet pipe is connected to the heat exchanger to pass the refrigerant into the accumulator; a refrigerant outlet pipe, one end of the refrigerant outlet pipe is connected to the accumulator, and the other end of the refrigerant outlet pipe is connected to the heat exchanger to pass the refrigerant in the accumulator into the heat exchanger; an expansion valve is arranged on the refrigerant inlet pipe to control the flow rate of the refrigerant inlet pipe; a pressure sensor is arranged on the compressor suction pipe of the outdoor unit of the air-conditioning system; an outlet pipe temperature sensor, the outlet pipe temperature sensor is arranged on the refrigerant outlet pipe; a control module, the control module is connected to the expansion valve, the pressure sensor and the outlet pipe temperature sensor for controlling the opening of the expansion valve according to the signals of the pressure sensor and the outlet pipe temperature sensor.

[0009] Furthermore, the energy storage structure also includes: a four-way valve, which is arranged on the refrigerant outlet pipe and located between the heat exchanger and the accumulator; wherein the first end and the second end of the four-way valve are both connected to the refrigerant outlet pipe, and the third end and the fourth end of the four-way valve are respectively connected to the outlet of the outdoor unit's compressor and the inlet of the gas-liquid separator.

[0010] Furthermore, the energy storage structure also includes an inlet pipe temperature sensor, which is arranged on the refrigerant inlet pipe.

[0011] Furthermore, the energy storage structure also includes an energy storage temperature sensor, which is arranged in the energy accumulator to measure the temperature of the energy storage fluid in the energy accumulator for storing cold energy.

[0012] The present application provides an air-conditioning system, which includes the above-mentioned energy storage structure; an outdoor unit arranged outdoors, the heat exchanger being arranged in the outdoor unit; a cooling release pipeline, the cooling release pipeline being connected to the energy storage structure to lead the refrigerant that has exchanged heat with the energy storage structure out of the energy storage structure; an indoor unit arranged indoors, the cooling release pipeline being connected to the refrigerant pipeline of the indoor unit, and the indoor unit being used to blow the air that has exchanged heat with the refrigerant that has passed through the refrigerant pipeline into the room.

[0013] The present application also provides a control method applicable to the above-mentioned energy storage structure, the control method including: determining which cold storage stage the energy storage structure is in; controlling the opening of the expansion valve according to the cold storage stage in which the energy storage structure is located using the measured values ​​of the outlet pipe temperature sensor and the pressure sensor; wherein the cold storage stage is divided according to the temperature of the energy storage fluid for storing cold energy in the accumulator.

[0014] Furthermore, the method for dividing the cold storage stage includes: recording the temperature T°C of the energy storage fluid in the accumulator detected by the energy storage temperature sensor set in the accumulator within a continuous detection cycle; comparing T°C with a first threshold value A°C and a second threshold value B°C; if T<A is not always satisfied within a continuous detection cycle, it is in stage I; if T<A is always satisfied and T<B is not always satisfied within a continuous detection cycle, it is in stage II; if T<B is always satisfied within a continuous detection cycle, it is in stage III; wherein the detection cycle is x seconds, and A>B.

[0015] Furthermore, x=40, A=2, B=0.

[0016] Furthermore, the control method includes: setting a target low pressure and a target superheat, and adjusting the opening of the expansion valve according to the target low pressure and the target superheat.

[0017] Furthermore, the control method includes: in stage I, setting the target low pressure to the difference (TC)°C between the temperature T°C of the energy storage fluid and the first preset temperature C°C, and setting the target superheat to the second preset temperature D°C; in stage II, setting the target low pressure to the third preset temperature E°C, and setting the target superheat to F°C; wherein C>|E|, D>F; and, in stage I, limiting the target low pressure to a minimum not lower than the second preset temperature E°C; when T≥(E+C), the target low pressure is the difference (TC)°C between the temperature T°C of the energy storage fluid and the first preset temperature C°C; when T<(E+C)°C, the target low pressure is the second preset temperature E°C.

[0018] Furthermore, C=15, D=5, E=-4, and F=2.

[0019] Furthermore, the method for adjusting the opening of the expansion valve includes: controlling the opening of the expansion valve according to the temperature deviation value; wherein, in stage I, the temperature deviation value = [(temperature in the refrigerant outlet pipe - temperature in the refrigerant inlet pipe) - target superheat]; in stage II, the temperature deviation value = temperature in the refrigerant outlet pipe - target low pressure.

[0020] Furthermore, in Phase I,

[0021] Furthermore, M=5, N=15.

[0022] Furthermore, in Phase II, y<M,z<N.

[0023] Furthermore, y=1, z=3.

[0024] Furthermore, in phase II, the detection period is extended from x seconds to x2 seconds, wherein x2>x.

[0025] Furthermore, x2=80.

[0026] Furthermore, the method for controlling the opening of the expansion valve includes: performing multiple judgments within a continuous detection cycle, and if the difference between the temperature in the refrigerant outlet pipe and the target low pressure is always not equal to the target superheat, the expansion valve is actuated; otherwise, the expansion valve does not actuate. Beneficial effects:

[0027] According to the cold storage expansion valve control method proposed in this application, the superheat and low pressure in the cold storage process can be reasonably controlled to achieve efficient cold storage in the ice storage multi-unit system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 is a schematic structural diagram of an energy storage structure used in an embodiment of the present application;

[0029] FIG2 is a schematic diagram of temperature changes of the energy storage fluid in the accumulator used in an embodiment of the present application;

[0030] FIG3 is a schematic diagram of the temperature change of the refrigerant in the refrigerant outlet pipe and the refrigerant inlet pipe used in the embodiment of the present application;

[0031] FIG4 is a flow chart of a control method used in an embodiment of the present application;

[0032] FIG5 is a schematic structural diagram of the air-conditioning system used in an embodiment of the present application in the cold storage stage;

[0033] FIG6 is a structural diagram of the air-conditioning system used in an embodiment of the present application in the cooling release stage.

[0034] Among them, the above-mentioned drawings include the following figure marks: 10, heat exchanger; 20, accumulator; 3, refrigerant inlet pipe; 4, refrigerant outlet pipe; 5, expansion valve; 6, pressure sensor; 7, outlet pipe temperature sensor; 8, inlet pipe temperature sensor; 9, compressor suction pipe; 2, cooling release pipeline; 1, four-way valve; 11, compressor; 12, gas-liquid separator. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0036] According to an embodiment of the present application, an energy storage structure is provided, referring to Figures 1 to 4, including: a heat exchanger 10; an accumulator 20; a refrigerant inlet pipe 3, one end of the refrigerant inlet pipe 3 is connected to the accumulator 20, and the other end of the refrigerant inlet pipe 3 is connected to the heat exchanger 10 to pass the refrigerant into the accumulator 20; a refrigerant outlet pipe 4, one end of the refrigerant outlet pipe 4 is connected to the accumulator 20, and the other end of the refrigerant outlet pipe 4 is connected to the heat exchanger 10 to pass the refrigerant in the accumulator 20 into the heat exchanger 10; an expansion valve 5, arranged on the refrigerant inlet pipe 3 to control the flow rate of the refrigerant inlet pipe 3; a pressure sensor 6, arranged on the compressor suction pipe 9 of the outdoor unit of the air-conditioning system; an outlet pipe temperature sensor 7, the outlet pipe temperature sensor 7 is arranged on the refrigerant outlet pipe 4; a control module, the control module is signal-connected to the expansion valve 5, the pressure sensor 6 and the outlet pipe temperature sensor 7 to control the opening of the expansion valve 5 according to the signals of the pressure sensor 6 and the outlet pipe temperature sensor 7.

[0037] With the above-mentioned setting, the pressure value measured by the pressure sensor 6 is used as a reference basis to calculate the heat exchange efficiency of the accumulator 20. Since the minimum pressure of the fluid in the pipeline is generally stable, and the temperature of the fluid will be affected by the different lengths and shapes of the pipeline and cause losses, therefore, in the heat storage structure, simply using the difference between the outlet temperature and the inlet temperature to control the refrigerant flow is not accurate enough. Using the pressure value for calculation can overcome the above-mentioned problem, thereby improving the heat exchange efficiency of the refrigerant and solving the problem of low heat exchange efficiency of the existing cold storage device.

[0038] The energy storage structure of the present application also includes a four-way valve 1, which is arranged on the refrigerant outlet pipe 4 and located between the heat exchanger 10 and the accumulator 20; wherein the first end and the second end of the four-way valve 1 are both connected to the refrigerant outlet pipe 4, and the third end and the fourth end of the four-way valve 1 are respectively connected to the outlet of the outdoor unit's compressor 11 and the inlet of the gas-liquid separator 12, and the inlet of the compressor 11 and the outlet of the gas-liquid separator 12 are connected through the compressor suction pipe 9.

[0039] Specifically, the refrigerant entering the inlet of the refrigerant outlet pipe 4 will pass through the first and second ends of the four-way valve 1, the gas-liquid separator 12, the compressor 11, and the third and fourth ends of the four-way valve 1 in sequence, and then reach the heat exchanger 10.

[0040] In the energy storage structure of this embodiment, the energy storage structure further includes an inlet pipe temperature sensor 8, which is disposed on the refrigerant inlet pipe 3. In this way, in some accumulators with simple piping arrangements, or in some operating conditions with low temperature loss, the temperature difference can still be used to determine the required cooling capacity, making the energy storage structure more comprehensive.

[0041] Specifically, the outlet pipe temperature sensor 7 is located at the inlet of the refrigerant outlet pipe 4 , and the inlet pipe temperature sensor 8 is located at the outlet of the refrigerant inlet pipe 3 .

[0042] The energy storage structure of this embodiment further includes an energy storage temperature sensor disposed within the accumulator 20 to measure the temperature of the energy storage fluid used to store cold energy within the accumulator 20. Thus, the energy storage temperature sensor is used to determine the state of the energy storage fluid within the accumulator 20 in order to control the flow rate.

[0043] The air-conditioning system of this embodiment includes an outdoor unit in which the above-mentioned energy storage structure is arranged outdoors, and the heat exchanger 10 is arranged in the outdoor unit; a cooling release pipeline 2, which is connected to the energy storage structure to lead the refrigerant that has exchanged heat with the energy storage structure out of the energy storage structure; an indoor unit arranged indoors, the cooling release pipeline 2 is connected to the refrigerant pipeline of the indoor unit, and the indoor unit is used to blow the air that has exchanged heat with the refrigerant that has passed through the refrigerant pipeline into the room.

[0044] Specifically, referring to FIG5 , in the cold storage stage, the heat exchanger 10 cools down the energy storage fluid in the energy accumulator 20 , thereby achieving cold storage.

[0045] Referring to Figure 6 , during the cooling phase, the refrigerant in cooling pipe 2 exchanges heat with the energy storage fluid through the energy storage structure before exchanging heat with the air in the indoor unit. The heat-exchanged air is then delivered to the indoor unit. The flow direction of the refrigerant in cooling pipe 2 is indicated by the arrows in the figure.

[0046] The control method of this embodiment is applicable to the above-mentioned energy storage structure. The control method includes: determining which cold storage stage the energy storage structure is in; and controlling the opening of the expansion valve 5 based on the cold storage stage the energy storage structure is in using the measured values ​​of the outlet pipe temperature sensor 7 and the pressure sensor 6. The cold storage stages are divided according to the temperature of the energy storage fluid used to store cold energy in the accumulator 20.

[0047] In the control method of this embodiment, the cold storage stage division method includes: recording the temperature T°C of the energy storage fluid in the accumulator detected by the energy storage temperature sensor provided in the accumulator 20 within a continuous detection cycle; comparing T with a first threshold value A°C and a second threshold value B°C; if T < A is not always satisfied within a continuous detection cycle, the cold storage stage is in stage I; if T < A is always satisfied and T < B is not always satisfied within a continuous detection cycle, the cold storage stage is in stage II; if T < B is always satisfied within a continuous detection cycle, the cold storage stage is in stage III; wherein the detection cycle is x seconds and A > B.

[0048] In the control method of this embodiment, the control method includes: setting a target low pressure and a target superheat, and adjusting the opening of the expansion valve 5 according to the target low pressure and the target superheat.

[0049] Specifically, the target low voltage is modified every time a detection cycle passes.

[0050] In the control method of this embodiment, the control method includes: in stage I, setting the target low pressure to the difference (TC)°C between the temperature T°C of the energy storage fluid and the first preset temperature C°C, and setting the target superheat to the second preset temperature D°C; in stage II, setting the target low pressure to a third preset temperature E°C, and setting the preset temperature target superheat to a fourth preset temperature F°C; wherein C>|E|, D>F; and, in stage I, limiting the target low pressure to a minimum of not less than E°C; when the temperature T of the energy storage fluid is ≥(E+C), the target low pressure is controlled according to (TC)°C; when T<(E+C), the target low pressure is set according to E°C.

[0051] Specifically, E is the unit setting parameter, which has been set before leaving the factory. It means the lower limit of the low pressure in stage I and stage II. The target low pressure in both stage I and stage II cannot be less than E.

[0052] In the control method of this embodiment, the method for adjusting the opening of the expansion valve 5 includes: the opening of the expansion valve 5 is controlled according to the temperature deviation value; wherein, in stage I, the temperature deviation value = [(temperature in the refrigerant outlet pipe 4 - temperature in the refrigerant inlet pipe 3) - target superheat]; in stage II, the temperature deviation value = temperature in the refrigerant outlet pipe 4 - target low pressure.

[0053] Specifically, the temperature in the refrigerant outlet pipe 4 is the temperature detected by the outlet pipe temperature sensor 7 , and the temperature in the refrigerant inlet pipe 3 is the temperature detected by the inlet pipe temperature sensor 8 .

[0054] In the control method of this embodiment, in stage I,

[0055] In the control method of this embodiment, in phase II,

[0056] Among them, y<M; z<N.

[0057] In the control method of this embodiment, the control method of the opening of the expansion valve 5 includes: performing multiple judgments in a continuous detection cycle, if the difference between the temperature in the refrigerant outlet pipe 4 and the target low pressure is always not equal to the target superheat, the expansion valve is actuated; otherwise, the expansion valve 5 does not actuate.

[0058] The accumulator used in the system is filled with a phase-change energy storage material, and the refrigerant flows in the coil, exchanging heat with the phase-change energy storage material filled therein to achieve cold storage or release. The phase-change energy storage material used in this embodiment is water or ice.

[0059] Specifically, the phase change energy storage material in the accumulator 20 is the energy storage fluid, and the refrigerant is able to flow in the refrigerant inlet pipe 3 and the refrigerant outlet pipe 4. When the refrigerant passes through the accumulator 20, it will exchange heat with the energy storage fluid in the accumulator 20.

[0060] The accumulator 20 is also provided with a temperature sensing package or other forms of accumulator temperature sensors for measuring the temperature of the accumulator 20 and feeding back the temperature as an electrical signal to the control unit for data processing.

[0061] The control method of this embodiment is described as follows:

[0062] 1. Distinguishing the cold storage stage

[0063] First, it is necessary to distinguish the extent of the cold storage process. This proposal divides the cold storage stage according to whether it is frozen, as shown in Figure 2. In stage I, the refrigerant exchanges heat with water (i.e., the energy storage fluid), exchanges cold energy to the water, and gradually reduces the water temperature. The water has not yet frozen in this stage. In stage II, the water temperature drops to the freezing point, and the water gradually freezes to form an ice-water mixture. Theoretically, the temperature of the ice-water mixture should be at 0°C, but the actual temperature sensing element (i.e., the energy storage temperature sensor) feedback at this stage fluctuates repeatedly around 0°C and is not constant. In stage III, all the water has frozen, and the refrigerant exchanges heat with the ice, exchanges cold energy to the ice, and continues to reduce the temperature of the ice.

[0064] In order to reasonably distinguish the above three stages, the temperature feedback from the temperature sensing element (i.e., the energy storage temperature sensor) built into the accumulator 20 is used for judgment. Taking into account the fluctuation of the detected temperature, the stages are divided in this way:

[0065] (a) If T℃<A℃ is not satisfied throughout a continuous detection cycle (x seconds), it is in stage I;

[0066] (b) If T℃<A℃ is always satisfied and T℃<B℃ is not always satisfied during a continuous detection cycle, it is in stage II;

[0067] (c) If T℃<B℃ is always satisfied during a continuous detection cycle, it is in stage III.

[0068] The recommended value for x is 40, the recommended value for A is 2, and the recommended value for B is 0. This way, even if the water temperature detection results fluctuate, it is still possible to determine whether there is ice.

[0069] Furthermore, since the refrigerant stores cold energy in ice during Stage III, actual testing results show that once the ice storage period ends, the ice temperature rapidly rises to 0°C, causing the stored cold energy to be rapidly lost to the environment. Therefore, this stage should be avoided as much as possible. Therefore, in actual operation, the system can be shut down when condition (c) is detected. Therefore, the remainder of this application will be explained based solely on Stages I and II.

[0070] 2. Setting of target low pressure and target superheat

[0071] Conventional air-cooled indoor units have fixed target low pressure and target superheat. However, in the energy storage structure of this application, if a fixed target low pressure, such as -4°C, is used, then in Phase I, when the water temperature is still high, the heat exchange temperature difference will be very large, resulting in a very high refrigerant temperature at the outlet of the accumulator 20. After returning to the compressor, the exhaust gas temperature will be too high, causing a malfunction. Therefore, it is necessary to set different target low pressure and target superheat according to the different cold storage stages.

[0072] In stage I, the target low pressure is set equal to the detected water temperature -C°C, and the target superheat is set to D°C.

[0073] In stage II, the target low pressure is set to E°C and the target superheat is set to F°C.

[0074] In general, it is assumed that C>|E| and D>F.

[0075] The recommended value for C is 15, the recommended value for D is 5, the recommended value for E is -4, and the recommended value for F is 2.

[0076] Among them, there are the following two settings:

[0077] (a) To ensure a smooth transition in setting the target low pressure, the target low pressure must not fall below E°C during Phase I. Thus, during Phase I, when the water temperature is ≥ (E+C)°C, the target low pressure is equal to the water temperature - C°C. When the water temperature is < (E+C)°C, the target low pressure is E°C.

[0078] (b) In Phase II, because the refrigerant pipeline is too long, far longer than that of a conventional air-cooled indoor unit, the pressure loss is greater, and the pressure at the refrigerant inlet pipe 3 is significantly higher than the pressure at the refrigerant outlet pipe 4. Therefore, the refrigerant saturation temperatures at the two locations are different. If "temperature deviation value = temperature inside the refrigerant outlet pipe 4 - temperature inside the refrigerant inlet pipe 3" is used as the criterion for refrigerant superheat control at this time, it will cause the temperature inside the refrigerant outlet pipe 4 - local saturation temperature to be too large, and the refrigerant will actually be severely overheated. Therefore, this proposal recommends using "temperature deviation value = temperature inside the refrigerant outlet pipe 4 - target low pressure" as the superheat criterion, that is, comparing "temperature deviation value = temperature inside the refrigerant outlet pipe 4 - target low pressure" with the target superheat to control the opening of the expansion valve 5.

[0079] For the value of setting data, there is the following analysis:

[0080] (a) In Phase I, the temperature difference between the refrigerant and the ice is approximately C°C, controlled by the target low pressure. In Phase II, the temperature difference is approximately |E|°C. Since C > |E| under normal circumstances, the heat exchange temperature difference in Phase I is greater than that in Phase II. This design is based on the fact that increasing the heat exchange temperature difference in Phase I helps the water temperature drop more quickly, allowing for a quicker transition to Phase II and the onset of freezing. In Phase II, experimental results show that, after a certain heat exchange temperature difference has been established, further reducing the low pressure has little effect on enhancing freezing, while significantly increasing energy consumption. Therefore, maintaining a certain target low pressure is sufficient.

[0081] (b) In Phase I, the target superheat is D°C, and in Phase II, the target superheat is F°C. Generally, D is set to > F because the heat exchange temperature difference in Phase I is greater than in Phase II, and water has a greater heat transfer capacity than ice. Therefore, the refrigerant superheat at refrigerant outlet pipe 4 is expected to be greater.

[0082] 3. Superheat fuzzy control

[0083] When a temperature sensing element is used in the energy storage structure, not only the temperature detected in the water / ice fluctuates, but also the temperature in the refrigerant outlet pipe 4 and the temperature in the refrigerant inlet pipe 3 fluctuate. When the target low pressure and the opening of the expansion valve 5 are stabilized, as shown in Figure 3, the temperature detection value of the water / ice will continue to fluctuate within the range of ±1°C, resulting in the temperature in the refrigerant outlet pipe 4 - the target low pressure and the target superheat being difficult to be completely equal. The frequent operation of the expansion valve 5 to meet the target of superheat regulation will cause damage to the valve body of the expansion valve 5.

[0084] Therefore, a superheat fuzzy control method was proposed. Expansion valve 5 is activated only when the refrigerant outlet pipe temperature minus the target low pressure consistently meets the target superheat within a continuous detection cycle. This prevents expansion valve 5 from actuating if the superheat briefly fluctuates, resulting in a slight fluctuation in the temperature deviation.

[0085] Adjusting the opening of expansion valve 5 directly affects the refrigerant circulation rate and is an important control method for the cold storage process. In conventional air-cooled indoor units, the opening of the expansion valve is controlled by the temperature deviation value = [(temperature in refrigerant outlet pipe 4 - temperature in refrigerant inlet pipe 3) - target superheat]. A common control method is to modify the target opening of expansion valve 5 every certain detection period (x seconds):

[0086] M is preferably 5, and N is preferably 15.

[0087] Under the manipulation of this control method, the opening of the expansion valve 5 will be opened 5 steps when the temperature deviation value = 1°C; and closed 15 steps when the temperature deviation value = -1°C. This method can be applied to stage I, but in stage II, during the freezing process, since the heat exchange pipes (including the refrigerant inlet pipe 3, the refrigerant outlet pipe 4 and the pipes in the accumulator 20 for the refrigerant to flow through) are long, and the heat transfer thermal resistance of the ice is large, these two factors together lead to a large thermal inertia. When the expansion valve 5 is actuated, it takes a long time for its regulating effect to be reflected in the temperature in the refrigerant outlet pipe 4. Therefore, a large-scale action of the expansion valve 5 will make it difficult to stabilize the refrigerant outlet pipe 4, and the expansion valve 5 will act repeatedly. Therefore, it is necessary to reduce the opening of the expansion valve 5 to adjust the sensitivity to the temperature deviation value. The following two measures can be taken:

[0088] (a) Reduce the adjustment range. In Phase II, combined with the previously mentioned "controlling the opening of the expansion valve 5 by comparing 'temperature deviation value = temperature in the refrigerant outlet pipe 4 - target low pressure' with the target superheat", the adjustment range is changed as follows:

[0089] Where y < 5, z < 15. The recommended values ​​are y = 1, z = 3.

[0090] (b) Extend the detection period. In Phase II, extend the detection period from x seconds to x2, where x2>x and the recommended value of x2 is 80.

[0091] These two adjustment measures can be used separately or simultaneously.

[0092] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in a sequence other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0093] Optionally, the specific examples in this embodiment may refer to the examples described in the above embodiments, and this embodiment will not be described in detail here.

[0094] The serial numbers of the above embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0095] In the above embodiments of the present application, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments.

[0096] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. An energy storage structure, characterized in that: include: Heat exchanger (10); Accumulator (20); A refrigerant inlet pipe (3), one end of which is connected to the accumulator (20), and the other end of which is connected to the heat exchanger (10) so as to allow the refrigerant to flow into the accumulator (20); A refrigerant outlet pipe (4), one end of the refrigerant outlet pipe (4) being connected to the accumulator (20), and the other end of the refrigerant outlet pipe (4) being connected to the heat exchanger (10) so as to pass the refrigerant in the accumulator (20) into the heat exchanger (10); An expansion valve (5) is arranged on the refrigerant inlet pipe (3) to control the flow rate of the refrigerant inlet pipe (3); A pressure sensor (6) is arranged on a compressor suction pipe (9) of an outdoor unit of an air conditioning system; An outlet pipe temperature sensor (7), wherein the outlet pipe temperature sensor (7) is arranged on the refrigerant outlet pipe (4); A control module, wherein the control module is signal-connected to the expansion valve (5), the pressure sensor (6) and the outlet pipe temperature sensor (7) so as to control the opening of the expansion valve (5) according to the signals of the pressure sensor (6) and the outlet pipe temperature sensor (7).

2. The energy storage structure according to claim 1, characterized in that: The energy storage structure further comprises: a four-way valve (1), wherein the four-way valve (1) is arranged on the refrigerant outlet pipe (4) and is located between the heat exchanger (10) and the energy accumulator (20); The first end and the second end of the four-way valve (1) are connected to the refrigerant outlet pipe (4), and the third end and the fourth end of the four-way valve (1) are respectively connected to the outlet of the compressor (11) of the outdoor unit and the inlet of the gas-liquid separator (12).

3. The energy storage structure according to claim 1, characterized in that: The energy storage structure also includes an inlet pipe temperature sensor (8), and the inlet pipe temperature sensor (8) is arranged on the refrigerant inlet pipe (3).

4. The energy storage structure according to claim 1, characterized in that: The energy storage structure also includes an energy storage temperature sensor, which is arranged in the energy accumulator (20) to measure the temperature of the energy storage fluid in the energy accumulator (20) for storing cold energy.

5. An air conditioning system, characterized in that: The air conditioning system comprises: The energy storage structure according to any one of claims 1 to 4; An outdoor unit is arranged outdoors, and the heat exchanger (10) is arranged in the outdoor unit; A cooling release pipeline (2), the cooling release pipeline (2) being connected to the energy storage structure so as to lead the cooling medium that has passed through the energy storage structure for heat exchange out of the cooling release pipeline (2) of the energy storage structure; An indoor unit is arranged indoors, the cooling release pipeline (2) is connected to the refrigerant pipeline of the indoor unit, and the indoor unit is used to blow the air after heat exchange with the refrigerant passing through the refrigerant pipeline into the room.

6. A control method, applicable to the energy storage structure according to any one of claims 1 to 4, characterized in that: The control method comprises: Determining which cold storage stage the energy storage structure is in; According to the cold storage stage of the energy storage structure, the opening of the expansion valve (5) is controlled by using the measured values ​​of the outlet pipe temperature sensor (7) and the pressure sensor (6); The cold storage stage is divided according to the temperature of the energy storage fluid for storing cold energy in the energy accumulator (20).

7. The control method according to claim 6, characterized in that: The method for dividing the cold storage stage includes: In a continuous detection cycle, recording the temperature T°C of the energy storage fluid in the energy storage device (20) detected by the energy storage temperature sensor disposed in the energy storage device (20); comparing T°C with a first threshold value A°C and a second threshold value B°C; If T<A is not satisfied in a continuous detection cycle, it is in stage I; If T<A is always satisfied and T<B is not always satisfied in a continuous detection cycle, it is in stage II; If T<B is always satisfied in a continuous detection cycle, it is in stage III; wherein the detection cycle is x seconds and A>B.

8. The control method according to claim 7, characterized in that: x=40, A=2, B=0.

9. The control method according to claim 7, characterized in that: The control method comprises: A target low pressure and a target superheat are set, and the opening of the expansion valve (5) is adjusted according to the target low pressure and the target superheat.

10. The control method according to claim 9, characterized in that: The control method comprises: In the stage I, the target low pressure is set to the difference (TC)°C between the temperature T°C of the energy storage fluid and the first preset temperature C°C, and the target superheat is set to the second preset temperature D°C; In the stage II, the target low pressure is set to a third preset temperature E°C, and the target superheat is set to a fourth preset temperature F°C; Among them, C>|E|, D>F; and, in the stage I, the target low pressure is limited to be no lower than the second preset temperature E℃; when T≥(E+C), the target low pressure is the difference (TC)℃ between the temperature T℃ of the energy storage fluid and the first preset temperature C℃; when T<(E+C), the target low pressure is the second preset temperature E℃.

11. The control method according to claim 10, characterized in that: C=15, D=5, E=-4, F=2.

12. The control method according to claim 10, characterized in that: The method for adjusting the opening degree of the expansion valve (5) comprises: The opening degree of the expansion valve (5) is controlled according to the temperature deviation value; wherein, In the stage I, the temperature deviation value = [(the temperature in the refrigerant outlet pipe (4) - the temperature in the refrigerant inlet pipe (3)) - the target superheat]; In the stage II, the temperature deviation value = the temperature in the refrigerant outlet pipe (4) - the target low pressure.

13. The control method according to claim 12, characterized in that: In the stage I, 14. The control method according to claim 13, characterized in that: M=5,N=15.

15. The control method according to claim 13, characterized in that: In the Phase II, 16. The control method according to claim 15, characterized in that: y=1,z=3.

17. The control method according to claim 13 or 15, characterized in that: In the phase II, the detection period is extended from x seconds to x2 seconds, wherein x2>x.

18. The control method according to claim 17, characterized in that: x2＝80。 19. The control method according to any one of claims 12 to 18, characterized in that: The method for controlling the opening degree of the expansion valve (5) comprises: Performing multiple determinations within a continuous detection cycle, if the difference between the temperature in the refrigerant outlet pipe (4) and the target low pressure is always not equal to the target superheat, the expansion valve (5) is actuated; Otherwise, the expansion valve (5) does not operate.

Images