Air conditioning system with controllable air injection valve and control method thereof

Abstract

The application provides a method for controlling a gas supplement valve in an air conditioning system, which is characterized by the following steps: step one, judging whether gas supplement is needed, if not, closing the gas supplement valve, and if yes, going to the next step; step two, obtaining the dryness of refrigerant entering the flash-type economizer; and step three, controlling the gas supplement valve according to the dryness. The application, based on the evaporation cooling pressure difference and the economizer liquid level, does not change the existing structure design of the air conditioning system, and controls the opening and closing of the gas supplement valve by further obtaining the dryness of refrigerant entering the flash-type economizer, thereby solving the problem of unnecessary opening and closing of the gas supplement valve caused by improper setting of the evaporation cooling pressure difference, and thus more accurately controlling the opening and closing of the gas supplement valve according to the operating condition and the unit state.

Description

Technical Field

[0001] This application relates to an air conditioning system, and more particularly to an air conditioning system having a controllable make-up air valve and a control method thereof.

[0002] Background section

[0003] In current air conditioning systems, the technical solutions for controlling the make-up gas valve include: controlling the make-up gas valve through the pressure difference (or pressure ratio) between the condenser and evaporator, controlling the make-up gas valve through the pressure difference between the economizer and evaporator, or controlling the opening and closing of the make-up gas valve through the make-up gas superheat. The method of controlling the opening and closing of the make-up gas valve through the make-up gas superheat is mostly used in plate heat exchanger economizers.

[0004] This application Figure 2 The diagram illustrates the pressure-enthalpy of a two-stage centrifugal compressor refrigeration cycle in the prior art. The horizontal axis represents the enthalpy (h) of the fluid, and the vertical axis represents the pressure (p) of the fluid. Point 1 represents the state of the first-stage suction port of compressor 101; point 2 represents the state of the first-stage discharge port of compressor 101; point 3 represents the state after the saturated gaseous refrigerant (point 9) in economizer 104 is mixed with the first-stage discharge (point 2) of compressor 101; point 4 represents the state of the second-stage discharge port of compressor 101; point 5 represents the outlet state of condenser 102 (including the subcooler); point 6 represents the inlet state of economizer 104 (the enthalpy of point 6 can be considered equal to that of point 5); point 7 represents the state of saturated liquid refrigerant in economizer 104; point 8 represents the inlet state of evaporator 107; and point 9 represents the state of saturated gaseous refrigerant in economizer 107.

[0005] In the scheme of controlling the opening and closing of the make-up gas valve through pressure difference (or pressure ratio), when the pressure difference is very small and below a certain set value, the make-up gas valve will close; when the pressure difference exceeds a certain set value, the make-up gas valve will open, thereby realizing the function of make-up gas to increase enthalpy. The purpose of the above control scheme is: First, when the pressure difference is very small, the pressure difference between the condenser and the flash economizer, and the pressure difference between the flash economizer and the evaporator, is even smaller, which causes insufficient opening of the first-stage and second-stage throttling valves and insufficient liquid supply, resulting in excessively low evaporator pressure or insufficient cooling capacity; Second, from the present application... Figure 2 It can be seen that when the pressure difference is small, such as in applications where the chilled water outlet temperature is high, the evaporation pressure increases, and the position of point 6 inside the economizer is closer to the left saturation line, that is, the saturated steam dryness is small (the water content is large). At this time, the gas replenishment has little effect on performance, and when the gas replenishment valve is open, the pressure of the economizer is low, which poses a risk of insufficient liquid supply from the liquid phase throttle valve and liquid carryover during gas replenishment. In this case, the gas replenishment valve can be closed. Summary of the Invention

[0006] Based on the inventor's observations and analysis, although the above... Figure 2The scheme shown, which uses the pressure difference between the evaporator, economizer (flash tank), and condenser to control the opening and closing of the make-up gas valve, has some merit, but also some shortcomings. For example, the pressure difference setting is mostly based on test experience; the same setting cannot be applied to all operating conditions, nor can it directly reflect the steam dryness within the flash economizer. If the pressure difference is set too low, the make-up gas valve may open unnecessarily, increasing the risk of insufficient liquid supply and liquid carryover during make-up gas operation. If the pressure difference is set too high, the make-up gas valve will close, failing to achieve the enthalpy-increasing function, thus reducing the unit's performance.

[0007] Therefore, according to the first aspect of this application, a method for controlling a gas replenishment valve in an air conditioning system is provided, the air conditioning system comprising: a compressor, a condenser, a flash economizer, a gas replenishment valve, and an evaporator, characterized in that the control method comprises the following steps: S01, determining whether gas replenishment is required; if gas replenishment is not required, closing the gas replenishment valve; if gas replenishment is required, proceeding to step S02; S02, obtaining the dryness of the refrigerant entering the flash economizer; S03, controlling the gas replenishment valve according to the dryness.

[0008] According to the first aspect of this application, the gas replenishment valve is an on / off valve, capable of replenishing gas by opening the gas replenishment valve and stopping gas replenishment by closing the gas replenishment valve; in step S03, controlling the gas replenishment valve further includes the following steps: when the obtained dryness is less than the lower limit of the dryness threshold, the gas replenishment valve is closed; when the obtained dryness is greater than the upper limit of the dryness threshold, the gas replenishment valve is opened; when the obtained dryness is greater than the lower limit of the dryness threshold and less than the upper limit of the dryness threshold, the gas replenishment valve is not adjusted.

[0009] According to the first aspect of this application, the gas replenishment valve is a regulating valve, which can adjust the gas replenishment speed by adjusting the opening of the gas replenishment valve; in step S03, controlling the gas replenishment valve further includes the following steps: calculating the opening of the gas replenishment valve based on the obtained dryness, and adjusting the opening of the gas replenishment valve.

[0010] According to a first aspect of this application, the step S03 further includes the following steps: calculating the opening and closing speed of the air supply valve based on the obtained dryness, and controlling the opening and closing speed of the air supply valve.

[0011] According to a first aspect of this application, the step S03 of controlling the gas supply valve further includes the following steps: obtaining the pressure difference between the evaporator and the condenser, calculating the opening degree of the gas supply valve based on the pressure difference between the evaporator and the condenser, and adjusting the opening degree of the gas supply valve.

[0012] According to the first aspect of this application, the determination of whether gas replenishment is required in step S01 further includes the following steps: obtaining the pressure difference between the evaporator and the condenser as a first pressure difference, obtaining the pressure difference between the evaporator and the flash economizer as a second pressure difference, obtaining the liquid level of the flash economizer, and obtaining the dryness of the refrigerant entering the flash economizer; when the first pressure difference is less than a first minimum pressure difference value, or the second pressure difference is less than a second minimum pressure difference value, or the liquid level of the flash economizer is greater than a maximum liquid level limit, or the dryness of the flash economizer is less than a lower limit of the dryness threshold, gas replenishment is not required; when the first pressure difference is not less than the first minimum pressure difference value, and the second pressure difference is not less than the second minimum pressure difference value, and the liquid level of the flash economizer is not greater than the maximum liquid level limit, and the dryness of the refrigerant entering the flash economizer is not less than the lower limit of the dryness threshold, gas replenishment is required.

[0013] According to a first aspect of this application, the step of calculating the opening degree of the air replenishment valve further includes the following steps: when the obtained dryness decreases, the opening degree of the air replenishment valve decreases; when the obtained dryness increases, the opening degree of the air replenishment valve increases.

[0014] According to a first aspect of this application, the step of calculating the switching speed of the air replenishment valve further includes the following steps: when the obtained dryness is greater than the upper limit of the dryness threshold, the switching speed of the air replenishment valve is slowed down; when the obtained dryness is less than the upper limit of the dryness threshold but greater than the lower limit of the dryness threshold, the switching speed of the air replenishment valve is increased; and when the obtained dryness is less than the lower limit of the dryness threshold, the air replenishment valve is closed.

[0015] According to a first aspect of this application, the method is characterized in that, in step S02, when obtaining the dryness of the refrigerant entering the flash economizer, the following steps are performed: obtaining the enthalpy of the liquid at the condenser outlet from an enthalpy parameter index table based on the pressure of the condenser and the temperature of the liquid at the condenser outlet; and obtaining the dryness of the refrigerant entering the flash economizer from a dryness parameter index table based on the pressure of the flash economizer and the enthalpy of the liquid at the condenser outlet.

[0016] According to a first aspect of this application, the flash economizer and the compressor's air inlet are in controllable fluid communication via the air inlet valve.

[0017] According to a second aspect of this application, an air conditioning system is provided, the air conditioning system comprising: a compressor, a condenser, a flash economizer, a gas filler valve, an evaporator, and a controller, characterized in that: the controller controls the gas filler valve in accordance with the method for controlling the gas filler valve in the air conditioning system described in the first aspect of this application. Attached Figure Description

[0018] These and other features and advantages of this application can be better understood by reading the following detailed description with reference to the accompanying drawings, throughout which the same reference numerals denote the same parts or the same steps, wherein:

[0019] Figure 1 A schematic block diagram of the components of the air conditioning system 100 of this application is shown;

[0020] Figure 2 The pressure-enthalpy diagram of a two-stage centrifugal compressor refrigeration cycle in the prior art is shown;

[0021] Figure 3 Controls are shown Figure 1 The flowchart 300 shows the air supply valve 105 in the air conditioning system 100 shown.

[0022] Figure 4 It shows Figure 3 The specific process of step 304 in the flowchart 300 shown;

[0023] Figure 5 It shows Figure 3 The first embodiment of the specific process of step 308 in the flowchart 300 shown;

[0024] Figure 6 It shows Figure 3 The second embodiment of the specific process of step 308 in the flowchart 300 shown;

[0025] Figure 7 It shows Figure 3 The third embodiment of the specific process of step 308 in the flowchart 300 shown;

[0026] Figure 8 A block diagram of the controller 108 in the air conditioning system 100 of this application is shown, illustrating the specific components and connections of the controller 108. Detailed Implementation

[0027] Figure 1 A schematic block diagram of the components of the air conditioning system 100 (chilled water unit system) of this application is shown to illustrate the main components of the air conditioning system of this application.

[0028] like Figure 1As shown, the chiller system includes a multi-stage centrifugal compressor 101, a condenser 102, a primary throttling valve 103, a flash economizer 104, an economizer air supply valve 105, a secondary throttling valve 106, an evaporator 107, and a controller 108. In addition, to collect various parameters in the air conditioning system 100, this application also includes a condenser pressure sensor 112, a condenser outlet liquid temperature sensor 114, an economizer pressure sensor 116, an economizer liquid level sensor 117, and an evaporator pressure sensor 118 in the air conditioning system 100.

[0029] In this application, the output 131 of the condenser pressure sensor 112, the output 132 of the condenser outlet temperature sensor 114, the output 134 of the economizer pressure sensor 116, the output 136 of the economizer level sensor 117, and the output 138 of the evaporator pressure sensor 118 are connected to the controller 108 to provide the controller 108 with the required sensor parameters. The combined use of these sensor parameters enables the controller 108 to control the opening and closing or the degree of opening of the gas supply valve 105 more effectively, more accurately, and more sensitively through the control line 142.

[0030] refer to Figure 1 The refrigerant circulation loop sequentially connects a multi-stage centrifugal compressor 101, a condenser 102, a first-stage expansion valve 103, a flash economizer 104, a second-stage expansion valve 106, and an evaporator 107. The upper part of the flash economizer 104 is connected to the intermediate stage of the multi-stage centrifugal compressor 101 via a make-up valve 105. The discharge port of the compressor 101 is fluidly connected to the inlet of the condenser 102, the outlet of the condenser 102 is fluidly connected to the inlet of the first-stage expansion valve 103, the outlet of the first-stage expansion valve 103 is fluidly connected to the inlet of the flash economizer 104, the liquid outlet of the flash economizer 104 is fluidly connected to the inlet of the second-stage expansion valve 106, the outlet of the second-stage expansion valve 106 is fluidly connected to the inlet of the evaporator 107, and the outlet of the evaporator 107 is fluidly connected to the suction port of the compressor 101. In addition, the gas outlet of the flash economizer 104 is connected to the inlet of the make-up air valve 105, and the outlet of the make-up air valve 105 is connected to the intermediate stage make-up air port of the compressor 101, thereby enabling controllable fluid communication between the flash economizer 104 and the intermediate stage make-up air port of the compressor 101 through the make-up air valve 105.

[0031] The refrigerant is compressed to a high-pressure, high-temperature state in compressor 101 and then discharged into condenser 102. In condenser 102, the refrigerant exchanges heat with cooling water, releasing heat and condensing into a high-pressure, liquid state, which is then discharged into primary throttling valve 103. In primary throttling valve 103, the refrigerant is expanded and throttled into a medium-pressure two-phase state before flowing into flash economizer 104. In flash economizer 104, the liquid and gaseous refrigerants are separated: the liquid refrigerant flows out from the lower pipe of flash economizer 104 and is discharged into secondary economizer 104. In the flow valve 106; in the flash economizer 104, gaseous refrigerant flows out from the upper pipe of the economizer, passes through the make-up gas valve 105, and is discharged into the intermediate stage of the compressor 101, where it mixes with the exhaust gas from the first-stage impeller of the compressor 101; the liquid refrigerant discharged from the bottom of the flash economizer 104 into the second-stage throttling valve 106 is expanded and throttled again into a low-pressure two-phase state, and then flows into the evaporator 107 to exchange heat with the chilled water, absorbing heat and being evaporated into a low-pressure, gaseous state before returning to the compressor 101 from the suction port. After this low-pressure gaseous refrigerant is drawn into the compressor 101, it is compressed into a medium-pressure gas by the first-stage impeller, mixes with the medium-pressure gas from the make-up gas valve 105 in the intermediate stage, and is compressed into a high-pressure, high-temperature gas by the second-stage impeller before being discharged to the condenser 102 to complete the refrigerant cycle.

[0032] Therefore, the air conditioning system 100 of this application has two refrigerant circulation loops: the first refrigerant circulation loop 152 is connected in sequence to the multi-stage centrifugal compressor 101, condenser 102, first-stage throttle valve 103, flash economizer 104 and make-up gas valve 105, wherein gaseous refrigerant flows from the top of flash economizer 104 through make-up gas valve 105 to compressor 101; the second refrigerant circulation loop 154 ​​is connected in sequence to the multi-stage centrifugal compressor 101, condenser 102, first-stage throttle valve 103, flash economizer 104, second-stage throttle valve 106 and evaporator 107, wherein liquid refrigerant flows from the bottom of flash economizer 104 through throttle valve 106 to evaporator 107.

[0033] It is worth noting that currently common compressors are two-stage centrifugal compressors, meaning the compressor has two impellers. The first-stage impeller draws in refrigerant, compresses it, and discharges it to the second-stage impeller's inlet. The second-stage impeller then performs a second compression, thereby increasing the discharge pressure. The compressor has two refrigerant inlets: the main inlet is at the front of the first-stage impeller, connected to the evaporator; the make-up refrigerant inlet is between the first and second-stage impellers, connected to the economizer. When the make-up refrigerant valve is closed, the refrigerant only flows into the compressor from the main inlet, and it still undergoes compression by both the first and second-stage impellers, but functionally it is similar to a single-stage compressor. The make-up refrigerant control method provided in this application is applicable to all two-stage or multi-stage compressor units with flash economizer make-up refrigerant, as well as screw compressors. The embodiments in this application are illustrated using a two-stage centrifugal compressor as an example, but are not limited to two-stage centrifugal compressors.

[0034] Figure 3 Controls are shown Figure 1 The flowchart 300 shows the air supply valve 105 in the air conditioning system 100.

[0035] like Figure 3 As shown, in step 304, the controller 108 determines whether the air conditioning system 100 needs refrigerant replenishment. If the air conditioning system 100 needs refrigerant replenishment, the operation proceeds to step 306, where the controller 108 acquires the dryness parameter of the refrigerant entering the flash economizer 104 (the specific method for acquiring the dryness parameter is described in step 414). After completing step 306, the operation proceeds to step 308, where the refrigerant replenishment valve 105 is controlled and adjusted based on the dryness parameter acquired in step 306. If it is determined in step 304 that the air conditioning system 100 does not need refrigerant replenishment, the operation proceeds to step 310, and the refrigerant replenishment valve 105 is closed.

[0036] After completing step 308, the operation proceeds to step 302 and then re-enters step 304 to determine whether the air conditioning system 100 needs gas replenishment.

[0037] After completing step 310, the operation proceeds to step 312 to determine whether to shut down the system. If shutdown is selected, the operation proceeds to step 314 to shut down the system; if shutdown is not selected, the operation proceeds to step 302 and re-enters step 304 to determine whether the air conditioning system 100 needs gas replenishment.

[0038] Figure 4 It shows Figure 3 The specific process of step 304 in flowchart 300 is shown.

[0039] Before proceeding to step 402, the controller 108 has pre-collected and stored various parameters required to control the make-up air valve 105. Specifically, the controller 108 collects the pressure parameters of the condenser 102 through the output 131 of the condenser pressure sensor 112, the temperature parameters of the liquid at the outlet of the condenser 102 through the output 132 of the condenser outlet liquid temperature sensor 114, the pressure parameters of the flash economizer 104 through the output 134 of the economizer pressure sensor 116, the liquid level parameters of the flash economizer 104 through the output 136 of the economizer level sensor 117, and the pressure parameters of the evaporator 107 through the output 138 of the evaporator pressure sensor 118. Simultaneously, the controller 108 sets the first minimum pressure difference between the evaporator 107 and the condenser 102, the second minimum pressure difference between the evaporator 107 and the flash economizer 104, the maximum liquid level limit of the flash economizer 104, and the lower and upper limits of the dryness threshold of the flash economizer 104.

[0040] As an embodiment of this application, the first minimum pressure difference between the evaporator 107 and the condenser 102 is set to 200 kPa, the second minimum pressure difference between the evaporator 107 and the flash economizer 104 is set to 100 kPa, the maximum liquid level limit of the flash economizer 104 is set to 80%, the lower limit of the dryness threshold of the flash economizer 104 is set to 0.02, and the upper limit of the dryness threshold of the flash economizer 104 is set to 0.05.

[0041] After the controller 108 collects and sets the above parameters, it proceeds to step 402.

[0042] In step 402, the pressure difference between the evaporator 107 and the condenser 102 is obtained as the first pressure difference based on the collected pressure parameters of the condenser 102 and the evaporator 107.

[0043] After completing step 402, the operation proceeds to step 404.

[0044] In step 404, when the first pressure difference between the evaporator 107 and the condenser 102 is less than the set first minimum pressure difference value, the process proceeds to step 420, where the air conditioning system 100 does not need to replenish gas, and only needs to meet the throttling liquid supply requirement. When the first pressure difference between the evaporator 107 and the condenser 102 is not less than the set first minimum pressure difference value, the process proceeds to step 406.

[0045] In step 406, the pressure difference between the evaporator 107 and the flash economizer 104 is obtained as the second pressure difference based on the collected pressure parameters of the flash economizer 104 and the evaporator 107.

[0046] After completing step 406, the operation proceeds to step 408.

[0047] In step 408, when the second pressure difference between the evaporator 107 and the flash economizer 104 is less than the set second minimum pressure difference value, proceed to step 420, and the air conditioning system 100 does not need to be refilled with gas. When the second pressure difference between the evaporator 107 and the flash economizer 104 is not less than the set second minimum pressure difference value, proceed to step 410.

[0048] In step 410, the liquid level parameters of the flash economizer 104 are acquired.

[0049] After completing step 410, the operation proceeds to step 412.

[0050] In step 412, when the liquid level parameter of the flash economizer 104 is greater than the set maximum liquid level limit, the process proceeds to step 420, and the air conditioning system 100 does not need to be replenished with gas, thereby avoiding the risk of liquid carryover during gas replenishment. When the liquid level parameter of the flash economizer 104 is not greater than the set maximum liquid level limit, the process proceeds to step 414.

[0051] In step 414, the dryness parameter of the refrigerant entering the flash economizer 104 is obtained.

[0052] Specifically, referring to Table 1 (Enthalpy Parameter Index Table), the pressure parameters of condenser 102 and the temperature parameters of the liquid at the outlet of condenser 102 are used as coordinate values ​​in Table 1. The value at the intersection of the two coordinates is then used as the enthalpy value of the liquid at the outlet of condenser 102 under those pressure and temperature parameters. For example, when the pressure of condenser 102 is 1470 kPa and the temperature of the liquid at the outlet of condenser 102 is 26°C, the enthalpy value of the liquid at the outlet of condenser 102 is found to be 236 kJ / kg.

[0053] Referring to Table 2 (dryness parameter index table), the pressure parameters of the flash economizer 104 and the enthalpy parameters of the liquid at the outlet of the condenser 102 obtained from Table 1 are used as coordinate values ​​in Table 2. The value at the intersection of the two coordinates is used as the dryness parameter of the refrigerant entering the flash economizer 104 under the pressure and enthalpy parameters.

[0054] As an embodiment of this application, when the enthalpy of the liquid at the outlet of condenser 102 is 236 kJ / kg and the pressure of flash economizer 104 is 500 kPa, the dryness fraction is found to be 0.078. This dryness fraction parameter reflects the content of saturated steam within flash economizer 104. Tables 1 and 2 are shown below, where the unit of temperature is °C, the unit of pressure is kPa, and the unit of enthalpy is kJ / kg.

[0055] Table 1

[0056]

[0057] Table 2

[0058]

[0059] After completing step 414, the operation proceeds to step 416.

[0060] In step 416, if the dryness parameter of the refrigerant entering the flash economizer 104, obtained in step 414, is less than the set lower limit of the dryness threshold, the process proceeds to step 420. The air conditioning system 100 does not require refrigerant replenishment, thereby reducing the risk of insufficient refrigerant supply and refrigerant carryover caused by setting the first or second minimum pressure difference value too low or the maximum liquid level limit value too high. If the dryness parameter obtained in step 414 is not less than the set lower limit of the dryness threshold, the process proceeds to step 418, where the air conditioning system 100 requires refrigerant replenishment.

[0061] It is worth noting that the above process for determining whether the air conditioning system 100 needs gas replenishment includes eight steps: 402, 404, 406, 408, 410, 412, 414, and 416. Steps 402 and 404 are the first judgment conditions, steps 406 and 408 are the second judgment conditions, steps 410 and 412 are the third judgment conditions, and steps 414 and 416 are the fourth judgment conditions. For those skilled in the art, the order of judgment for the first judgment conditions (steps 402 and 404), the second judgment conditions (steps 406 and 408), the third judgment conditions (steps 410 and 412), and the fourth judgment conditions (steps 414 and 416) is not fixed and can be arbitrarily adjusted. For example, the fourth judgment condition (steps 414 and 416) can be judged first, and the first judgment condition (steps 402 and 404) can be judged last.

[0062] After completing step 418, the operation proceeds to step 306 (see above). Figure 3 (Description).

[0063] Figure 5 It shows Figure 3 The first embodiment of the specific process of step 308 in the flowchart 300 shown.

[0064] exist Figure 5 In the embodiment shown, the gas supply valve 105 is a switch valve that can supply gas to the air conditioning system 100 by opening the gas supply valve 105 and stop supplying gas by closing the gas supply valve 105.

[0065] In step 502, when the dryness parameter of the refrigerant entering the flash economizer 104, obtained in step 306, is less than the set lower limit of the dryness threshold, the operation proceeds to step 506, and the make-up gas valve 105 is closed. When the dryness parameter obtained in step 306 is greater than the set upper limit of the dryness threshold, the operation proceeds to step 504, and the make-up gas valve 105 is opened. When the dryness parameter obtained in step 306 is between the set upper and lower limits of the dryness threshold, the operation proceeds to step 508, and the make-up gas valve 105 is not adjusted, that is, no operation is performed on the make-up gas valve 105.

[0066] After completing steps 504, 506 and 508, proceed to step 302 and re-enter step 304 to determine whether the air conditioning system 100 needs gas replenishment.

[0067] Figure 6 It shows Figure 3 The second embodiment of the specific process of step 308 in the flowchart 300 shown.

[0068] exist Figure 6 In the embodiment shown, the air replenishment valve 105 is a regulating valve, which can adjust the air replenishment speed by adjusting the opening of the air replenishment valve 105.

[0069] In step 602, the opening degree of the gas replenishment valve 105 is calculated based on the dryness of the refrigerant entering the flash economizer 104 obtained in step 306. Specifically, when the obtained dryness decreases, the opening degree of the gas replenishment valve 105 decreases, and when the obtained dryness increases, the opening degree of the gas replenishment valve 105 increases.

[0070] As one embodiment of this application, the opening degree of the air supply valve 105 can be linearly related to the obtained dryness. As one embodiment of this application, the linear relationship between the opening degree of the air supply valve 105 and the dryness is detailed in Table 3 below.

[0071] Table 3

[0072] Dryness 0.02 0.06 0.10 Air supply valve opening 0 50％ 100％

[0073] It is worth mentioning that, for those skilled in the art, the opening degree of the gas-replenishing valve may not be linearly related to the dryness of the refrigerant, depending on the valve characteristics of different gas-replenishing valves. For example, the opening degree of the gas-replenishing valve may be positively correlated with the dryness of the refrigerant rather than in a nonlinear relationship.

[0074] After completing step 602, proceed to step 604, and adjust the opening of the air supply valve 105 according to the opening of the air supply valve 105 calculated in step 602.

[0075] After completing step 604, proceed to step 302 and re-enter step 304 to determine whether the air conditioning system 100 needs gas replenishment.

[0076] Figure 7 It shows Figure 3 The third embodiment of the specific process of step 308 in the flowchart 300 shown.

[0077] exist Figure 7In the embodiment shown, the gas replenishment valve 105 is a regulating valve, which can adjust the gas replenishment speed by adjusting the opening size of the gas replenishment valve 105. At the same time, the opening and closing speed of the gas replenishment valve 105 can be calculated based on the dryness of the refrigerant entering the flash economizer 104.

[0078] In step 702, the opening and closing speed of the make-up gas valve 105 is calculated based on the dryness of the refrigerant entering the flash economizer 104 obtained in step 306. Specifically, when the obtained dryness is greater than the upper limit of the set dryness threshold, the opening and closing speed of the make-up gas valve 105 is slower or reduced to avoid the make-up gas valve operating too quickly, causing drastic changes in pressure and liquid level inside the flash economizer 104; when the obtained dryness is between the upper limit and the lower limit of the set dryness threshold, the opening and closing speed of the make-up gas valve 105 is faster or increased; when the obtained dryness is less than the lower limit of the set dryness threshold, the make-up gas valve 105 is closed (see the description of step 416 above).

[0079] As an embodiment of this application, when the dryness parameter of the refrigerant entering the flash economizer 104 is greater than 0.05 (i.e., the upper limit of the dryness threshold), the gas supply valve 105 is adjusted (opened or closed) by 5% each time, and after waiting for 2 minutes, it is adjusted (opened or closed) by 5% until the target opening value is reached; when the dryness parameter of the flash economizer 104 is between 0.02 and 0.05 (i.e., between the lower limit and the upper limit of the dryness threshold), the gas supply valve 105 is directly adjusted (opened or closed) to the target opening value; when the dryness parameter of the flash economizer 104 is less than 0.02 (i.e., the lower limit of the dryness threshold), the gas supply valve 105 is closed.

[0080] While calculating the opening and closing speed of the gas supply valve 105 in step 702, step 704 is performed simultaneously. In step 704, the controller 108 acquires the pressure difference between the evaporator 107 and the condenser 102. After completing step 704, the process proceeds to step 706.

[0081] In step 706, the opening degree of the gas supply valve 105 is calculated based on the pressure difference between the evaporator 107 and the condenser 102 obtained in step 704. Specifically, when the pressure difference between the evaporator 107 and the condenser 102 decreases, the opening degree of the gas supply valve 105 decreases, thereby increasing the pressure drop in the gas supply line and increasing the pressure of the flash economizer 104; when the pressure difference between the evaporator 107 and the condenser 102 increases, the opening degree of the gas supply valve 105 increases, thereby decreasing the pressure drop in the gas supply line and decreasing the pressure of the flash economizer 104. When the pressure difference between the evaporator 107 and the condenser 102 is greater than the maximum pressure difference value, the gas supply valve 105 is fully opened.

[0082] As one embodiment of this application, the maximum pressure difference between the evaporator 107 and the condenser 102 is set to 300 kPa, and the opening degree of the gas supply valve 105 can be linearly related to the pressure difference between the evaporator 107 and the condenser 102 within the range of 200 kPa to 300 kPa. As one embodiment of this application, the linear relationship between the opening degree of the gas supply valve and the pressure difference is detailed in Table 4 below.

[0083] Table 4

[0084] Cooling pressure difference (kPa) 200 250 300 Air supply valve opening 0 50％ 100％

[0085] It is worth mentioning that, for those skilled in the art, the opening degree of the make-up air valve may not be linearly related to the pressure difference between the evaporator and the condenser, depending on the valve characteristics of different make-up air valves. For example, the opening degree of the make-up air valve may be positively correlated with the pressure difference between the evaporator and the condenser rather than in a nonlinear relationship.

[0086] After completing steps 702 and 706, proceed to step 708, where the opening of the air supply valve 105 is adjusted based on the switching speed of the air supply valve 105 calculated in step 702 and the opening parameter of the air supply valve 105 calculated in step 706.

[0087] After completing step 708, proceed to step 302 and re-enter step 304 to determine whether the air conditioning system 100 needs gas replenishment.

[0088] Figure 8 A block diagram of the controller 108 in the air conditioning system of this application is shown, illustrating the specific components and connections of the controller 108. The controller 108 is capable of storing and executing... Figures 3-7 The process flow shows the procedures, stored procedures, and calls as follows: Figures 3-7 The parameters required for the process.

[0089] like Figure 8 As shown, the controller 108 includes a bus 802, a processor 804, a memory 806, an input interface 808, and an output interface 810. The processor 804, memory 806, input interface 808, and output interface 810 are connected to the bus 802. The processor 804 can read programs (or instructions) from the memory 806 and execute the programs (or instructions) to process data; the processor 804 can also write data or programs (or instructions) into the memory 806. The memory 806 can store programs (instructions) or data. By executing the instructions in the memory 806, the processor 804 can control the memory 806, the input interface 808, and the output interface 810. In this application, the memory 806 is capable of storing instructions for execution... Figure 3 and Figure 4The process shown includes the procedure and the operating parameters required to execute the procedure; the memory 806 is also capable of storing an index table for obtaining the liquid enthalpy at the outlet of the condenser 102 (see Table 1 above) and an index table for obtaining the refrigerant dryness entering the flash economizer (see Table 2 above).

[0090] The input interface 808 is configured to receive sensor parameters from the condenser pressure sensor 112, the condenser outlet temperature sensor 114, the economizer pressure sensor 116, the economizer level sensor 117, and the evaporator pressure sensor 118 respectively via outputs 131, 132, 134, 136, and 138, and convert the data of these parameters into signals that can be recognized by the processor 804 and store them in the memory 806.

[0091] The processor 804 is configured to calculate or read relevant parameters controlling the opening and closing or the degree of opening of the air supply valve 105 according to a program stored in the memory 806. As an example, this is accomplished as follows: Figures 3-7 The program and parameters of the process shown can be stored in memory 806, and processor 804 can read the parameters from memory 806 and execute the program.

[0092] The output interface 810 is configured to receive parameters related to the opening or closing or opening degree of the air supply valve 105 from the processor 804, convert these parameters into control signals for the air supply valve 105, and control the opening or closing or opening degree of the air supply valve 105 by receiving executable control signals from the output interface 810 through the control line 142.

[0093] The air supply valve control method of this application has the following advantages over the existing air supply valve control methods:

[0094] Based on the evaporation-cooling pressure difference and the economizer liquid level, this application does not change the existing structural design of the air conditioning (chilled water unit) system. By further obtaining the dryness of the refrigerant entering the flash economizer to jointly control the opening and closing of the make-up gas valve, it solves the problem of unnecessary opening and closing of the make-up gas valve caused by improper evaporation-cooling pressure difference setting. Thus, it can more accurately control the opening and closing of the make-up gas valve according to the operating conditions and unit status.

[0095] Although this application has been described with reference to examples of the embodiments outlined above, various alternatives, modifications, variations, improvements, and / or substantially equivalents, whether known or currently or soon to be foreseen, will likely be apparent to those skilled in the art. Furthermore, the technical effects and / or technical problems described herein are exemplary and not limiting; therefore, the disclosures herein may be used to solve other technical problems and have other technical effects and / or can solve other technical problems. Thus, the examples of embodiments of this application as set forth above are intended to be illustrative and not limiting. Various changes can be made without departing from the spirit or scope of this application. Therefore, this application is intended to include all known or previously developed alternatives, modifications, variations, improvements, and / or substantially equivalents.

Claims

1. A method for controlling a gas supply valve in an air conditioning system, the air conditioning system (100) comprising: The compressor (101), condenser (102), flash economizer (104), make-up valve (105), and evaporator (107) are characterized in that the method includes the following steps: S01, Obtain parameters, the parameters including at least the dryness of the refrigerant entering the flash economizer (104); S02, based on the parameters obtained in step S01, including at least the dryness of the refrigerant entering the flash economizer (104), determine whether gas replenishment is needed. If gas replenishment is not needed, close the gas replenishment valve (105). If gas replenishment is needed, proceed to step S03; and S03, based on the dryness level, control the opening and closing, opening degree or switching speed of the air supply valve (105).

2. The method for controlling the air supply valve in an air conditioning system according to claim 1, characterized in that: The gas replenishment valve (105) is an on / off valve, which can replenish gas by opening the gas replenishment valve (105) and stop replenishing gas by closing the gas replenishment valve (105); In step S03, controlling the opening and closing of the air supply valve (105) includes the following steps: When the obtained dryness is less than the lower limit of the dryness threshold, the gas supply valve (105) is closed. When the obtained dryness is greater than the upper limit of the dryness threshold, the gas supply valve (105) is opened; and When the obtained dryness is between the lower limit of the dryness threshold and the upper limit of the dryness threshold, the gas replenishment valve (105) is not adjusted.

3. The method for controlling the air supply valve in an air conditioning system according to claim 1, characterized in that: The air replenishment valve (105) is a regulating valve, which can adjust the air replenishment speed by adjusting the opening of the air replenishment valve (105); In step S03, controlling the opening degree of the air supply valve (105) includes the following steps: (i) Calculate the opening degree of the air supply valve (105) based on the obtained dryness; and (ii) Adjust the opening of the air supply valve (105) according to the calculated opening of the air supply valve (105).

4. The method for controlling the air supply valve in an air conditioning system according to claim 1, characterized in that: In step S03, controlling the opening and closing speed of the air supply valve (105) includes the following steps: (i) Calculate the opening and closing speed of the supplementary air valve (105) based on the obtained dryness; and (ii) Control the opening and closing speed of the air supply valve (105) according to the calculated opening and closing speed of the air supply valve (105).

5. The method for controlling the air supply valve in an air conditioning system according to claim 4, characterized in that: In step S03, controlling the air supply valve (105) further includes the following steps: (iii) Obtain the pressure difference between the evaporator (107) and the condenser (102); (iv) Calculate the opening degree of the make-up air valve (105) based on the pressure difference between the evaporator (107) and the condenser (102); and (v) Adjust the opening of the air supply valve (105) based on the calculated switching speed and opening degree of the air supply valve (105).

6. The method for controlling the air supply valve in an air conditioning system according to claim 1, characterized in that: In step S01, obtaining the parameter includes at least the following steps: The pressure difference between the evaporator (107) and the condenser (102) is obtained as the first pressure difference, the pressure difference between the evaporator (107) and the flash economizer (104) is obtained as the second pressure difference, the liquid level of the flash economizer (104) is obtained, and the dryness of the refrigerant entering the flash economizer (104) is obtained. In step S02, determining whether air replenishment is needed includes at least the following steps: When the first pressure difference is less than the first minimum pressure difference value, or the second pressure difference is less than the second minimum pressure difference value, or the liquid level of the flash economizer (104) is greater than the maximum liquid level limit, or the dryness of the refrigerant in the flash economizer (104) is less than the lower limit of the dryness threshold, it is determined that no gas replenishment is required; and When the first differential pressure is not less than the first minimum differential pressure value, the second differential pressure is not less than the second minimum differential pressure value, the liquid level of the flash economizer (104) is not greater than the maximum liquid level limit, and the dryness of the refrigerant entering the flash economizer (104) is not less than the lower limit of the dryness threshold, it is determined that gas needs to be replenished.

7. The method for controlling the air supply valve in an air conditioning system as described in claim 3, characterized in that: In step (i): When the obtained dryness decreases, the opening degree of the air supply valve (105) decreases; and When the obtained dryness increases, the opening degree of the air supply valve (105) increases.

8. The method for controlling the air supply valve in an air conditioning system as described in claim 4, characterized in that: In step (i): When the obtained dryness is greater than the upper limit of the dryness threshold, the opening and closing speed of the air supply valve (105) is slowed down. When the obtained dryness is between the upper limit and the lower limit of the dryness threshold, the opening and closing speed of the air supply valve (105) increases. as well as When the obtained dryness is less than the lower limit of the dryness threshold, the air replenishment valve (105) is closed.

9. The method for controlling the air supply valve in an air conditioning system as described in claim 1, characterized in that: In step S01, the following steps are performed when obtaining the dryness of the refrigerant entering the flash economizer (104): (i) Obtain the enthalpy of the liquid at the outlet of the condenser (102) from the enthalpy parameter index table based on the pressure of the condenser (102) and the temperature of the liquid at the outlet of the condenser (102); and (ii) The dryness of the refrigerant entering the flash economizer (104) is obtained from the dryness parameter index table based on the pressure of the flash economizer (104) and the enthalpy of the liquid at the outlet of the condenser (102).

10. The method for controlling the air supply valve in an air conditioning system as described in claim 1, characterized in that: The flash economizer (104) and the compressor (101) are connected in a controllable fluid manner through the air supply valve (105).

11. An air conditioning system (100), comprising: The compressor (101), condenser (102), flash economizer (104), make-up valve (105), evaporator (107), and controller (108) are characterized by: The controller (108) controls the air supply valve (105) according to the method for controlling the air supply valve in the air conditioning system according to any one of claims 1-10.

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