Multi-split refrigerating unit and control method for uniform liquid distribution thereof

Abstract

The application discloses a multi-split refrigerating unit and a control method for uniform refrigerant distribution. The control method comprises the following steps: periodically detecting the temperature and pressure at the outlet of each evaporator; and controlling the flow direction of the adjusting pump between adjacent flow paths according to the range of the difference between the saturation temperatures corresponding to the outlet pressures of the adjacent evaporators, so as to automatically and uniformly distribute the refrigerant flow on the adjacent flow paths. According to the difference between the saturation temperatures corresponding to the outlet pressures of the adjacent flow paths and the range of the outlet superheat, the adjusting pump automatically and uniformly distributes the refrigerant flow of two pipes, so that the refrigerant is uniformly distributed under various working conditions, and the reliability of the unit operation is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the air conditioning technical field, and especially relates to a multi-split refrigeration unit and a control method for uniform distribution of refrigerant. BACKGROUND

[0002] In a multi-split system, one main unit is usually used to supply cooling to multiple terminals, typically a two-in-one refrigeration unit. In a multi-split system, a distribution device is a key part to achieve the distribution of refrigerant among multiple indoor units (or cold storage) according to demand. The distribution device usually includes a distributor, an electronic expansion valve and other components, which are used to control the flow of refrigerant into each indoor unit. The distributor uses the principles of gravity and inertia to achieve gas-liquid separation, ensuring that the refrigerant entering the evaporator reaches the designed dryness. The electronic expansion valve adjusts the refrigerant flow according to the signal of the indoor temperature sensor to meet the indoor cooling and heating load requirements. In the distributor, a distribution pipe is usually used to guide the distribution process. Due to the different lengths of the pipe for each indoor unit and the different environments used, it is easy to cause uneven distribution of the unit. Increasing the length of the distribution pipe within a certain range can significantly improve the uniformity of the distribution of refrigerant among multiple evaporators or indoor units, because the increase in the length of the distribution pipe helps to reduce the flow resistance and pressure loss of the refrigerant in the pipe, allowing the refrigerant to be more evenly distributed to each evaporator or indoor unit. With the increase in the length of the distribution pipe, the flow deviation gradually decreases. When the length of the distribution pipe is long enough, the flow of refrigerant in the pipe is more stable, thereby reducing the flow deviation. However, when the length of the distribution pipe increases to a certain extent, its effect on the flow deviation gradually slows down, because the flow resistance in the pipe is relatively small at this time, and further increasing the length of the distribution pipe has little effect on the flow distribution. In fact, the length of the distribution pipe is also limited by the installation site. The length of the distribution pipe is usually adjusted under certain working conditions in engineering, and then adjusted by the electronic expansion valve during operation of the unit. However, under extreme conditions, the electronic expansion valve adjustment is relatively uneven, which can cause one indoor unit to have too much distribution, serious frosting, lower low-pressure side pressure, shorten the service life of the compressor, and reduce the reliability of the unit. SUMMARY

[0003] The present application provides a multi-split refrigeration unit and a control method for uniform distribution of refrigerant to solve the technical problem of uneven distribution of indoor units in the prior art, thereby ensuring the reliability of the operation of the multi-split refrigeration unit.

[0004] The technical scheme adopted by the present application is to provide a multi-in-one refrigeration unit, which comprises N flow paths leading to terminal devices and branched from an outlet pipeline of a condenser, an electronic expansion valve and an evaporator are arranged on each flow path, outlet pipelines of the evaporators are merged and communicated with a suction pipeline of a compressor of the refrigeration unit, a branch path is arranged between adjacent flow paths, an adjusting pump is arranged on the branch path, and a controller of the refrigeration unit controls the adjusting pump to balance the flow of each evaporator according to the difference between the saturation temperatures corresponding to the outlet pressures of the evaporators in the adjacent flow paths and the outlet superheat.

[0005] In an embodiment, the multi-in-one refrigeration unit comprises two flow paths, a branch path is arranged between the inlet sections of the first flow path and the second flow path, and an adjusting pump is arranged on the branch path.

[0006] In another embodiment, the multi-in-one refrigeration unit comprises four flow paths, a branch path is arranged between the first flow path and the second flow path, a branch path is arranged between the second flow path and the third flow path, a branch path is arranged between the third flow path and the fourth flow path, and an adjusting pump is arranged on each branch path.

[0007] Further, a temperature sensor and a pressure sensor are arranged at the outlet end of the evaporator.

[0008] The present application also provides a uniform distribution control method for a multi-in-one refrigeration unit, which comprises the following steps.

[0009] Step 1. Detecting the temperature and pressure at the outlet of each evaporator according to a cycle;

[0010] Step 2. Controlling the flow direction of the adjusting pump between adjacent flow paths according to the range of the difference between the saturation temperatures corresponding to the outlet pressures of the adjacent evaporators, and automatically balancing the flow of the refrigerant in the adjacent flow paths.

[0011] Further, the step 2 comprises the following steps.

[0012] Comparing the saturation temperatures corresponding to the outlet pressures of the two evaporators in the adjacent flow paths, and opening the adjusting pump from the flow path with the greater saturation temperature to the flow path with the smaller saturation temperature, and entering the automatic adjustment mode of the electronic expansion valve;

[0013] When the absolute value of the difference between the saturation temperatures corresponding to the outlet pressures of the adjacent evaporators is less than or equal to 1, the electronic expansion valve exits the automatic adjustment mode, and the refrigeration unit enters the fine adjustment mode.

[0014] In a two-in-one refrigeration unit, the step 2 comprises the following steps.

[0015] When the difference between the saturation temperature corresponding to the first evaporator outlet pressure Pc1 and the saturation temperature corresponding to the second evaporator outlet pressure Pc2 is greater than 1, Pc1-Pc2>1, the regulating pump is opened from the first flow path to the second flow path;

[0016] When the difference between the saturation temperature corresponding to the second evaporator outlet pressure Pc2 and the saturation temperature corresponding to the first evaporator outlet pressure Pc1 is greater than 1, Pc2-Pc1>1, the regulating pump is opened from the second flow path to the first flow path;

[0017] When the absolute value of the difference between the saturation temperature corresponding to the first evaporator outlet pressure Pc1 and the saturation temperature corresponding to the second evaporator outlet pressure Pc2 is less than or equal to 1, |Pc1-Pc2|≤1, the electronic expansion valve exits the automatic adjustment, and the refrigerating unit enters the fine adjustment mode.

[0018] Further, when the regulating pump is opened from the first flow path to the second flow path, the operating power of the regulating pump is controlled according to the following ratio:

[0019] When the ratio of the difference between the saturation temperature corresponding to the first evaporator outlet pressure and the saturation temperature corresponding to the second evaporator outlet pressure in the nth cycle to the difference between the saturation temperature corresponding to the first evaporator outlet pressure and the saturation temperature corresponding to the second evaporator outlet pressure in the last cycle is greater than 1, (Pc1 n -Pc2 n ) / (Pc1 n-1 -Pc2 n-1 )>1, the opening power of the regulating pump is A times the current power;

[0020] When the ratio of the difference between the saturation temperature corresponding to the first evaporator outlet pressure and the saturation temperature corresponding to the second evaporator outlet pressure in the nth cycle to the difference between the saturation temperature corresponding to the first evaporator outlet pressure and the saturation temperature corresponding to the second evaporator outlet pressure in the last cycle is equal to 1, (Pc1 n -Pc2 n ) / (Pc1 n-1 -Pc2 n-1 )=1, the opening power W of the regulating pump is unchanged;

[0021] When the ratio of the difference between the saturation temperature corresponding to the first evaporator outlet pressure and the saturation temperature corresponding to the second evaporator outlet pressure in the nth cycle to the difference between the saturation temperature corresponding to the first evaporator outlet pressure and the saturation temperature corresponding to the second evaporator outlet pressure in the last cycle is less than 1, (Pc1 n -Pc2 n ) / (Pc1 n-1-Pc2 n-1 )<1, the opening power of the regulating pump is B times the current power.

[0022] Further, when the regulating pump is opened from the second flow path to the first flow path, the operating power of the regulating pump is controlled according to the following ratio:

[0023] When the difference between the saturation temperature corresponding to the second evaporator outlet pressure of the nth cycle and the saturation temperature corresponding to the first evaporator outlet pressure is greater than the difference between the saturation temperature corresponding to the second evaporator outlet pressure of the last cycle and the saturation temperature corresponding to the first evaporator outlet pressure, (Pc2 n -Pc1 n ) / (Pc2 n-1 -Pc1 n-1 )>1, the opening power of the regulating pump is A times of the current opening power;

[0024] When the difference between the saturation temperature corresponding to the second evaporator outlet pressure of the nth cycle and the saturation temperature corresponding to the first evaporator outlet pressure is equal to the difference between the saturation temperature corresponding to the second evaporator outlet pressure of the last cycle and the saturation temperature corresponding to the first evaporator outlet pressure, (Pc2 n -Pc1 n ) / (Pc2 n-1 -Pc1 n-1 )=1, the opening power W of the regulating pump is unchanged;

[0025] When the difference between the saturation temperature corresponding to the second evaporator outlet pressure of the nth cycle and the saturation temperature corresponding to the first evaporator outlet pressure is less than the difference between the saturation temperature corresponding to the second evaporator outlet pressure of the last cycle and the saturation temperature corresponding to the first evaporator outlet pressure, (Pc2 n -Pc1 n ) / (Pc2 n-1 -Pc1 n-1 )<1, the opening power of the regulating pump is B times of the current power.

[0026] Preferably, the A value is 0.95, and the B value is 1.03.

[0027] Further, the fine adjustment mode comprises calculating the outlet superheat of each evaporator, and adjusting the electronic expansion valve and the regulating pump according to the range of the outlet superheat.

[0028] Specifically, the fine adjustment mode comprises:

[0029] If the outlet superheat of the first evaporator and the second evaporator satisfies 7>T1>T2>4 or 7>T2>T1>4, the control mode of the refrigerating unit is unchanged, and the existing mode is maintained to operate;

[0030] If the outlet superheat of the first evaporator and the second evaporator satisfies: 7>T1>4>T2, the opening degree B2 of the second electronic expansion valve is reduced by 1%, and the opening power W of the regulating pump is maintained unchanged;

[0031] If the outlet superheat of the first evaporator and the second evaporator satisfies: 7>T2>4>T1, the opening degree B1 of the first electronic expansion valve is reduced by 1%, and the opening power W of the regulating pump is maintained unchanged;

[0032] If the outlet superheat of the first evaporator and the second evaporator satisfies: 4>T1>T2 or 4>T2>T1, the opening degree B1 of the first electronic expansion valve and the opening degree B2 of the second electronic expansion valve are reduced by 1%, and the opening power W of the regulating pump is maintained unchanged;

[0033] If the outlet superheat of the first evaporator and the second evaporator satisfies: T1>T2>10 or T2>T1>10, the opening degree B1 of the first electronic expansion valve and the opening degree B2 of the second electronic expansion valve are increased by 1%, and the opening power W of the regulating pump is maintained unchanged;

[0034] If the outlet superheat of the first evaporator and the second evaporator satisfies: T1>10>T2>4, the opening degree B1 of the first electronic expansion valve is increased by 1%, and the opening power W of the regulating pump is maintained unchanged;

[0035] If the outlet superheat of the first evaporator and the second evaporator satisfies: T2>10>T1>4, the opening degree B2 of the second electronic expansion valve is increased by 1%, and the opening power W of the regulating pump is maintained unchanged;

[0036] If the outlet superheat of the first evaporator and the second evaporator satisfies: T1>10>4>T2, the opening degree B1 of the first electronic expansion valve is increased by 2%, the opening degree B2 of the second electronic expansion valve is reduced by 1%, and the regulating pump is opened from the second flow path to the first flow path. At this time, it is judged whether the opening flow direction of the regulating pump is consistent with the original opening direction. If consistent, the opening power of the regulating pump is adjusted to 1.01 times of the current power. If not consistent, the opening power of the regulating pump is adjusted to 0.05 times of the total power of the regulating pump.

[0037] If the outlet superheat of the first evaporator and the second evaporator satisfies: T2>10>4>T1, the opening degree B2 of the second electronic expansion valve is increased by 2%, the opening degree B1 of the first electronic expansion valve is reduced by 1%, and the regulating pump is opened from the first flow path to the second flow path. At this time, it is judged whether the opening flow direction of the regulating pump is consistent with the original opening direction. If consistent, the opening power of the regulating pump is adjusted to 1.01 times of the current power. If not consistent, the opening power of the regulating pump is adjusted to 0.05 times of the total power of the regulating pump.

[0038] Further, the automatic adjustment opening degree B of the electronic expansion valve is: the current opening degree B NThe sum of the adjustment steps Sn1 in the nth period and Sn2 in the (n-1)th period, B = B N +Sn1+S12, where:

[0039] Sn1=(T1 n -5.5); Sn2=S1*[(T1 n -5.5) / (T1 n-1 -5.5)-1];

[0040] In the above formula: T1 n It is the outlet superheat of the nth period, T1 n-1 Export overheating in the (n-1)th cycle.

[0041] Compared with the prior art, the technical solution proposed in this invention has the following advantages:

[0042] The present invention adds a branch between adjacent flow paths, and adds a regulating pump on the branch. The regulating pump is used to balance the flow rate of the evaporator on the adjacent flow paths, thereby improving the uniformity of liquid distribution and refrigeration efficiency.

[0043] The liquid equalization control method proposed in this invention automatically detects parameters such as the outlet temperature and outlet pressure of each evaporator. Based on the difference in saturation temperature corresponding to the outlet pressure of the evaporators on adjacent flow paths and the range of outlet superheat, it automatically and evenly distributes the flow rate of the refrigerant in the two pipes by adjusting the pump, ensuring uniform liquid distribution under various operating conditions, maintaining a relatively consistent state of the indoor units in a multi-unit system, and ensuring the reliability of the unit operation. Attached Figure Description

[0044] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments, wherein:

[0045] Figure 1 This is a system diagram of an embodiment of the present invention;

[0046] Figure 2 yes Figure 1 A schematic diagram of the first flow path supplying liquid to the second flow path in the illustrated embodiment;

[0047] Figure 3 yes Figure 1 A schematic diagram of the second flow path supplying liquid to the first flow path in the illustrated embodiment;

[0048] Figure 4 This is a system diagram of another embodiment of the present invention;

[0049] Figure 5 This is a schematic block diagram of the homogenization control method proposed in this invention;

[0050] Figure 6 yes Figure 1 The flowchart of the regulating pump in the illustrated embodiment;

[0051] Figure 7 is Figure 1 Flow chart of the refrigeration unit entering the micro-adjustment mode in the embodiment shown.

[0052] wherein:

[0053] 1 compressor, 2 condenser, 3 gas-liquid separator, 4 branch, 5 regulating pump, 6 suction stop valve, 7 liquid supply stop valve, 10 first flow path, 11 first electronic expansion valve, 12 first evaporator, 20 second flow path, 21 first electronic expansion valve, 22 second evaporator;

[0054] B automatically adjusted opening degree;

[0055] B N current opening degree of the electronic expansion valve on the Nth flow path;

[0056] B1 current opening degree of the first electronic expansion valve;

[0057] B2 current opening degree of the second electronic expansion valve;

[0058] W opening power of the regulating pump;

[0059] W 调节 adjusting power of the regulating pump;

[0060] Wz total power of the regulating pump;

[0061] Tc1 outlet temperature of the first evaporator;

[0062] Tc2 outlet temperature of the second evaporator;

[0063] P1 outlet pressure of the first evaporator;

[0064] P2 outlet pressure of the second evaporator;

[0065] Pc1 saturation temperature corresponding to the outlet pressure of the first evaporator;

[0066] Pc2 saturation temperature corresponding to the outlet pressure of the second evaporator;

[0067] T1 outlet superheat of the first evaporator;

[0068] T2 outlet superheat of the second evaporator;

[0069] n detection period;

[0070] Sn1 adjusting step number of the electronic expansion valve in the nth period;

[0071] Sn2 adjusting step number of the electronic expansion valve in the n-1th period. DETAILED DESCRIPTION

[0072] In order to make the objects, technical solutions and advantages of the present application clearer, the following will be detailed with reference to the drawings and embodiments. It should be understood that the following specific embodiments are only used to explain the present application and do not limit the present application.

[0073] The terms used in the specification are only for describing the specific embodiments, and are not intended to limit the present application. Unless otherwise specified, the relative arrangement, numerical expressions and values of the components and steps set forth in these embodiments do not limit the scope of protection of the present application.

[0074] The techniques, methods and devices known to those skilled in the relevant art are not discussed in detail in the specification, but should be considered as part of the specification in appropriate cases. Any specific value in the specification should be interpreted as merely exemplary and not as limiting the present application.

[0075] For ease of description, the terms used in the specification to describe the position, such as "on", "left", "front", etc., are only used to describe the spatial positional relationship of a component with other components in the embodiments shown in the drawings, and when the component is placed in a different position, the relative position will change, therefore the positional relationship of the embodiments of the drawings should not be considered as limiting the present application.

[0076] In addition, it should be noted that the terms "first", "second", etc. used in the specification are only used to distinguish similar components, and there is no sequence, therefore it should not be understood as limiting the scope of protection of the present application.

[0077] The concept of the present application is to add a branch between adjacent flow paths leading to the evaporator, and a regulating pump is arranged on the branch, and the flow direction and power of the regulating pump are used to balance the flow to each evaporator.

[0078] The existing one-to-many refrigeration unit includes N flow paths leading to the end device from the condenser outlet pipeline, and an electronic expansion valve and an evaporator are arranged on each flow path, and the outlet pipelines of the evaporators are combined and communicated with the compressor suction pipeline of the refrigeration unit. The improvement point of the present application is to arrange a branch between adjacent flow paths, and a regulating pump is arranged on the branch, and the controller of the refrigeration unit controls the flow direction and power of the regulating pump according to the difference between the saturation temperatures corresponding to the outlet pressures of the evaporators in adjacent flow paths and the outlet superheat, so as to achieve the purpose of balancing the flow to each evaporator.

[0079] Figure 1The system diagram of the one-to-two refrigeration unit is shown, which is composed of an outdoor unit and an indoor unit. The outdoor unit comprises a compressor 1, a condenser 2 and a gas-liquid separator 3. The indoor unit comprises two flow paths, a first flow path 10 and a second flow path 20, which are branched from the refrigerant outlet pipeline of the condenser. The first flow path is provided with a first electronic expansion valve 11 and a first evaporator 12, and the second flow path is provided with a second electronic expansion valve 21 and a second evaporator 22. The outdoor unit and the indoor unit are connected through a suction cut-off valve 6 and a liquid supply cut-off valve 7. The first evaporator and the second evaporator provide cold energy to the indoor unit, and then the first flow path and the second flow path are combined and connected to the suction pipeline of the compressor.

[0080] In the refrigeration cycle, the refrigerant is compressed by the compressor 1 into a high-temperature and high-pressure gas, then is liquefied by heat release in the condenser 2 into a high-pressure and normal-temperature liquid, and then is divided into two paths. The refrigerant in the first flow path is throttled by the first electronic expansion valve 11 and then flows to the first evaporator 12 for cooling. The refrigerant in the second flow path is throttled by the second electronic expansion valve 21 and then flows to the second evaporator 22 for cooling. The refrigerant is evaporated and absorbs heat in the first evaporator and the second evaporator, and then is combined and returned to the compressor for circulation.

[0081] For control purposes, temperature sensors and pressure sensors are arranged at the outlet positions of the first evaporator 12 and the second evaporator 22 to detect the temperature and pressure of the refrigerant outlet of the first evaporator and the second evaporator.

[0082] To ensure uniform liquid distribution in the one-to-two refrigeration unit, the refrigeration unit provided by the present application is provided with a branch pipeline 4 between the inlet pipelines of the first flow path 10 and the second flow path 20, and an adjusting pump 5 is arranged on the branch pipeline. The controller of the refrigeration unit automatically detects the outlet temperature, outlet pressure and other parameters of each evaporator after liquid distribution, automatically balances the flow of the refrigerant on the first flow path and the second flow path according to the difference between the corresponding saturated temperatures of the outlet pressures of adjacent evaporators and the range of outlet superheat, and ensures uniform liquid distribution under various working conditions, maintains the relative consistency of the indoor heat exchanger of the one-to-two refrigeration unit, and ensures the reliability of the unit operation.

[0083] The current opening degree of the first electronic expansion valve 11 is B1, the current opening degree of the second electronic expansion valve 21 is B2, the initial opening degrees of the first electronic expansion valve and the second electronic expansion valve are determined according to the external environment and the internal environment working conditions (conventional technical means), the total power of the adjusting pump 5 is Wz, the current opening power is W, and the detection period is n. In this embodiment, the detection period is set to one minute, and the period can be adjusted according to the working conditions in actual work.

[0084] As shown in Figure 5 The uniform liquid distribution control method of the one-to-many refrigeration unit provided by the present application comprises:

[0085] Step 1. Detect the temperature and pressure of each evaporator outlet periodically;

[0086] Step 2. Control the flow direction and power of the regulating pump between adjacent flow paths according to the range of the difference between the saturation temperatures corresponding to the outlet pressures of adjacent evaporators, to automatically balance the flow of refrigerant in adjacent flow paths.

[0087] The step 2 includes:

[0088] Compare the saturation temperatures corresponding to the outlet pressures of two adjacent flow paths, and open the regulating pump from the flow path with the higher saturation temperature to the flow path with the lower saturation temperature;

[0089] When the absolute value of the difference between the saturation temperatures corresponding to the outlet pressures of two adjacent flow paths is less than or equal to 1, the electronic expansion valve exits automatic adjustment, and the refrigeration unit enters fine adjustment mode.

[0090] Figure 6 A control method flow chart for uniform distribution of a one-and-a-half refrigeration unit is shown, including the following steps:

[0091] First, detect the outlet temperature and pressure of the first evaporator and the second evaporator, and calculate the outlet superheat;

[0092] The outlet temperature Tc1 and outlet pressure P1 of the first evaporator 12 are detected by a temperature sensor and a pressure sensor, the corresponding saturation temperature Pc1 is calculated according to the outlet pressure P1, and the outlet superheat T1 of the first evaporator is calculated as T1 = Tc1 - Pc1. The outlet temperature Tc2 and outlet pressure P2 of the second evaporator 22 are measured, the corresponding saturation temperature Pc2 is calculated according to the outlet pressure P2, and the outlet superheat T2 of the second evaporator is calculated as T2 = Tc2 - Pc2.

[0093] Then, the flow direction of the regulating pump 5 on the branch is controlled according to the range of the difference between the saturation temperature Pc1 corresponding to the outlet pressure of the first evaporator and the saturation temperature Pc2 corresponding to the outlet pressure of the second evaporator, to automatically balance the flow of refrigerant in the first flow path and the second flow path, and the adjustment is divided into three cases:

[0094] I. When the difference between the saturation temperature Pc1 corresponding to the outlet pressure of the first evaporator and the saturation temperature Pc2 corresponding to the outlet pressure of the second evaporator is greater than 1, Pc1 - Pc2 > 1, the first and second electronic expansion valves enter automatic adjustment, at this time, the regulating pump 5 is opened from the first flow path 10 to the second flow path 20 (as shown in Figure 2 The direction of the subsequent regulating pump remains unchanged until the current adjustment is completed.

[0095] Then, the operating power of the regulating pump is controlled according to the following ratio:

[0096] The difference between the saturation temperature Pc1n corresponding to the outlet pressure of the first evaporator in the nth cycle and the saturation temperature Pc2n corresponding to the outlet pressure of the second evaporator is equal to the difference between the saturation temperature Pc1n corresponding to the outlet pressure of the first evaporator in the previous cycle and the saturation temperature Pc2n corresponding to the outlet pressure of the first evaporator in the previous cycle. n-1 The saturation temperature Pc2 corresponding to the outlet pressure of the second evaporator n-1 When the ratio of the differences is greater than 1, (Pc1n-Pc2n) / (Pc1n-1-Pc2n-1)>1, the starting power of the regulating pump 5 is A times the current power. In this embodiment, the value of A is 0.95.

[0097] The difference between the saturation temperature Pc1n corresponding to the outlet pressure of the first evaporator in the nth cycle and the saturation temperature Pc2n corresponding to the outlet pressure of the second evaporator is equal to the difference between the saturation temperature Pc1n corresponding to the outlet pressure of the first evaporator in the previous cycle and the saturation temperature Pc2n corresponding to the outlet pressure of the first evaporator in the previous cycle. n-1 The saturation temperature Pc2 corresponding to the outlet pressure of the second evaporator n-1 When the ratio of the differences is equal to 1, (Pc1n-Pc2n) / (Pc1n-1-Pc2n-1)=1, and the starting power of the regulating pump 5 is kept constant at the current starting power W.

[0098] The difference between the saturation temperature Pc1n corresponding to the outlet pressure of the first evaporator in the nth cycle and the saturation temperature Pc2n corresponding to the outlet pressure of the second evaporator is equal to the difference between the saturation temperature Pc1n corresponding to the outlet pressure of the first evaporator in the previous cycle and the saturation temperature Pc2n corresponding to the outlet pressure of the first evaporator in the previous cycle. n-1 The saturation temperature Pc2 corresponding to the outlet pressure of the second evaporator n-1 When the ratio of the differences is less than 1, (Pc1n-Pc2n) / (Pc1n-1-Pc2n-1)<1, the starting power of the regulating pump 5 is B times the current power. In this embodiment, the value of B is 1.03.

[0099] 2. When the difference between the saturation temperature Pc2 corresponding to the outlet pressure of the second evaporator and the saturation temperature Pc1 corresponding to the outlet pressure of the first evaporator is greater than 1, Pc2-Pc1>1, the first and second electronic expansion valves enter automatic adjustment, and the regulating pump 5 is opened from the second flow path 20 to the first flow path 10 (e.g., Figure 3 (As shown), the direction of the pump will not be changed during subsequent adjustments until the adjustment is completed.

[0100] Next, the pump's operating power is controlled and adjusted according to the following ratio:

[0101] The difference between the saturation temperature Pc2n corresponding to the outlet pressure of the second evaporator in the nth cycle and the saturation temperature Pc1n corresponding to the outlet pressure of the first evaporator is equal to the difference between the saturation temperature Pc2n corresponding to the outlet pressure of the second evaporator in the previous cycle and the saturation temperature Pc2n corresponding to the outlet pressure of the second evaporator in the previous cycle. n-1 The saturation temperature ratio Pc1 corresponding to the outlet pressure of the first evaporator n-1When the ratio of the differences is greater than 1, (Pc2n-Pc1n) / (Pc2 n-1 -Pc1 n-1 If the power of pump 5 is greater than 1, adjust the starting power of pump 5 to A times the current starting power. In this embodiment, the value of A is 0.95.

[0102] The difference between the saturation temperature Pc2n corresponding to the outlet pressure of the second evaporator in the nth cycle and the saturation temperature Pc1n corresponding to the outlet pressure of the first evaporator is equal to the difference between the saturation temperature Pc2n corresponding to the outlet pressure of the second evaporator in the previous cycle and the saturation temperature Pc2n corresponding to the outlet pressure of the second evaporator in the previous cycle. n-1 The saturation temperature ratio Pc1 corresponding to the outlet pressure of the first evaporator n-1 When the ratio of the differences is equal to 1, (Pc2n-Pc1n) / (Pc2n-1-Pc1n-1)=1, and the starting power of the regulating pump 5 is kept constant at the current starting power W.

[0103] The difference between the saturation temperature Pc2n corresponding to the outlet pressure of the second evaporator in the nth cycle and the saturation temperature Pc1n corresponding to the outlet pressure of the first evaporator is equal to the difference between the saturation temperature Pc2n corresponding to the outlet pressure of the second evaporator in the previous cycle and the saturation temperature Pc2n corresponding to the outlet pressure of the second evaporator in the previous cycle. n-1 The saturation temperature ratio Pc1 corresponding to the outlet pressure of the first evaporator n-1 When the ratio of the differences is less than 1, (Pc2n-Pc1n) / (Pc2n-1-Pc1n-1)<1, the starting power of the pump 5 is adjusted to be B times the current power. In this embodiment, the value of B is 1.03.

[0104] 3. When the absolute value of the difference between the saturation temperature Pc1 corresponding to the outlet pressure of the first evaporator and the saturation temperature Pc2 corresponding to the outlet pressure of the second evaporator is less than or equal to 1, |Pc1-Pc2|≤1, the electronic expansion valve exits automatic adjustment, and the refrigeration unit enters fine-tuning mode.

[0105] like Figure 7 As shown, the fine-tuning mode adjusts the opening of the electronic expansion valve and the power of the pump based on the relationship between the outlet superheat T1 of the first evaporator and the outlet superheat T2 of the second evaporator. Specifically, it includes nine operating modes:

[0106] If 7 > T1 ≥ T2 > 4 or 7 > T2 ≥ T1 > 4, the refrigeration unit control mode remains unchanged and the existing mode is maintained.

[0107] If 7>T1≥4>T2, the opening degree B2 of the second electronic expansion valve 12 is reduced by 1%, and the opening power W of the regulating pump 5 remains unchanged.

[0108] If 7>T2≥4>T1, the opening degree B1 of the first electronic expansion valve 11 is reduced by 1%, and the starting power W of the regulating pump 5 remains unchanged.

[0109] If 4≥T1≥T2 or 4≥T2≥T1, the opening degree B1 of the first electronic expansion valve 11 and the opening degree B2 of the second electronic expansion valve 21 are reduced by 1%, and the opening power W of the regulating pump 5 is maintained unchanged;

[0110] If T1≥T2≥10 or T2≥T1≥10, the opening degree B1 of the first electronic expansion valve 11 and the opening degree B2 of the second electronic expansion valve 21 are increased by 1%, and the opening power W of the regulating pump 5 is maintained unchanged;

[0111] If T1≥10≥T2≥4, the opening degree B1 of the first electronic expansion valve 11 is increased by 1%, and the opening power W of the regulating pump 5 is maintained unchanged;

[0112] If T2≥10≥T1≥4, the opening degree B2 of the second electronic expansion valve 21 is increased by 1%, and the opening power W of the regulating pump 5 is maintained unchanged;

[0113] If T1≥10≥4≥T2, the opening degree B1 of the first electronic expansion valve 11 is increased by 2%, the opening degree B2 of the second electronic expansion valve 21 is reduced by 1%, and the regulating pump 5 is opened from the second flow path to the first flow path. At this time, it is judged whether the opening flow direction of the regulating pump is consistent with the original opening direction. If the flow direction of the regulating pump is consistent with the original opening direction of the regulating pump, the opening power of the regulating pump 5 is adjusted to 1.01 times the current power, W 调节 = 1.01*W; if the regulating pump is closed or inconsistent with the original opening direction of the regulating pump, the opening power of the regulating pump 5 is adjusted to 0.05 times the total power of the regulating pump, W 调节 = 0.05Wz;

[0114] If T2≥10≥4≥T1, the opening degree B2 of the second electronic expansion valve 21 is increased by 2%, the opening degree B1 of the first electronic expansion valve 11 is reduced by 1%, and the regulating pump 5 is opened from the first flow path to the second flow path. At this time, it is judged whether the opening flow direction of the regulating pump is consistent with the original opening direction. If the flow direction of the regulating pump is consistent with the original opening direction of the regulating pump, the opening power of the regulating pump 5 is adjusted to 1.01 times the current opening power, W 调节 = 1.01*W, if the regulating pump is closed or inconsistent with the original opening direction of the regulating pump, the opening power of the regulating pump 5 is adjusted to 0.05 times the total power of the regulating pump, W 调节 = 0.05Wz.

[0115] After the above fine adjustment is completed, exit and wait for the next cycle to press Figure 6 the flow to control.

[0116] Automatic adjustment of electronic expansion valve: the automatic adjustment opening degree B of the electronic expansion valve on a flow path is the sum of the current opening degree B N of the flow path, the adjustment step number Sn1 of the nth cycle and the adjustment step number Sn2 of the n-1th cycle, B = BN +Sn1+S12, wherein: Sn1 = (T1 n - 5.5);

[0117] Sn2 = S1 * [(T1 n - 5.5) / (T1 n-1 - 5.5) - 1];

[0118] In the above formula: T1 n is the evaporator outlet superheat of the first flow path in the nth cycle, T1 n-1 is the evaporator outlet superheat of the first flow path in the (n-1)th cycle.

[0119] The automatic adjustment opening of the first electronic expansion valve 11 is the sum of the current opening Bl, the adjustment step number S11 of the first electronic expansion valve in the nth cycle, and the adjustment step number S12 of the first electronic expansion valve in the (n-1)th cycle, B = Bl + S11 + S12, wherein:

[0120] Bl is the current opening of the first electronic expansion valve;

[0121] S11 is the adjustment step number of the first electronic expansion valve in the nth cycle, S12 is the adjustment step number of the first electronic expansion valve in the (n-1)th cycle, and S11 and S12 vary according to the detected value;

[0122] S11 = (T1 n - 5.5), S12 = S1 * [(T1 n - 5.5) / (T1 n-1 - 5.5) - 1];

[0123] T1 n is the evaporator outlet superheat of the first flow path in the nth cycle, T1 n-1 is the evaporator outlet superheat of the first flow path in the (n-1)th cycle.

[0124] The automatic adjustment opening of the second electronic expansion valve 22 is the same as that of the first electronic expansion valve, equal to B2 + S21 + S22, wherein S21 is the adjustment step number of the second electronic expansion valve in the nth cycle, and S22 is the adjustment step number of the second electronic expansion valve in the (n-1)th cycle.

[0125] The two electronic expansion valves are controlled separately.

[0126] Figure 4The system diagram is another embodiment of the present application. The embodiment is a one-to-four refrigeration unit, including four flow paths from the condenser outlet pipeline to the terminal device. The first flow path 10 is provided with a first electronic expansion valve 11 and a first evaporator 12, the second flow path 20 is provided with a second electronic expansion valve 21 and a second evaporator 22, the third flow path 30 is provided with a third electronic expansion valve 31 and a third evaporator 32, and the fourth flow path 40 is provided with a fourth electronic expansion valve 41 and a fourth evaporator 42. The outlet pipelines of the evaporators are merged and communicated with the compressor suction pipeline of the refrigeration unit. A branch pipeline 4 is arranged between the adjacent flow paths, and an adjusting pump 5 is arranged on the branch pipeline. The controller of the refrigeration unit controls the flow of each adjusting pump to the evaporators according to the difference between the saturation temperatures corresponding to the outlet pressures of the evaporators on the adjacent flow paths and the mutual relationship of the outlet superheat degrees of the evaporators.

[0127] In the one-to-many case, the control of the adjusting pump is taken as a control unit for the adjacent flow paths, that is, Figure 4 the first flow path 10 and the second flow path 20 in the control unit, the second flow path and the third flow path 30 are a control unit, the third flow path and the fourth flow path 40 are a control unit, the second flow path 20 is adjacent to the first flow path 10 and the third flow path 30, the first flow path 10 and the third flow path 30 are not adjacent, a branch pipeline and an adjusting pump are arranged between the adjacent flow paths, and three adjusting pumps 5 are arranged in the embodiment. Each adjusting pump is a control unit, each control unit is independently controlled and does not affect each other, and the electronic expansion valves on each flow path are controlled according to their own conditions.

[0128] If multiple adjusting commands are received at the same time, for example, the first flow path 10 and the second flow path 20 enter the automatic mode, the adjusting pump flows from the second flow path 20 to the first flow path 10, the second flow path 20 and the third flow path 30 enter the automatic adjusting mode, the adjusting pump flows from the third flow path 30 to the second flow path 20, or the adjusting pump flows from the first flow path 10 to the second flow path 20 and the third flow path 30 to the second flow path 20, the direction of the adjusting pump does not change after entering the automatic adjusting mode, and only the power of the adjusting pump is adjusted according to the size of (Pc1 n-Pc2n) / (Pc1 n-1-Pc2n-1) until the current adjustment is completed.

[0129] The liquid equalization control method provided by the present application automatically detects the outlet temperature, outlet pressure and other parameters of each evaporator, automatically balances and distributes the flow of two pipelines through the adjusting pump according to the difference between the saturation temperatures corresponding to the outlet pressures of the evaporators on the adjacent flow paths and the range of the outlet superheat degree, ensures uniform liquid distribution under various working conditions, maintains the relative consistency of the indoor unit state of the one-to-many, and ensures the reliability of the operation of the unit.

[0130] The above merely describes specific embodiments of the present application. It should be noted that any modification, equivalent replacement and change made within the spirit and framework of the present application should be included in the protection scope of the present application.

Claims

1. A multi-split refrigeration unit, comprising N flow paths branching from the condenser outlet pipe to terminal devices, each flow path equipped with an electronic expansion valve and an evaporator, the outlet pipes of all evaporators converging and connected to the compressor suction pipe of the refrigeration unit, characterized in that, A branch is provided between adjacent flow paths, and a regulating pump is provided on the branch. The controller of the refrigeration unit controls the flow rate of the regulating pump to each evaporator in a balanced manner based on the difference in saturation temperature corresponding to the evaporator outlet pressure on the adjacent flow paths and the outlet superheat.

2. The multi-split refrigeration unit as described in claim 1, characterized in that, It includes two flow paths, with a branch path between the inlet sections of the first and second flow paths, and a regulating pump is installed on the branch path.

3. The multi-split refrigeration unit as described in claim 1, characterized in that, It includes four flow paths. There is a branch between the first and second flow paths, a branch between the second and third flow paths, and a branch between the third and fourth flow paths. Each branch is equipped with a regulating pump.

4. The multi-split refrigeration unit as described in claim 2 or 3, characterized in that, The outlet end of the evaporator is equipped with a temperature sensor and a pressure sensor.

5. The uniform liquid distribution control method for a multi-split refrigeration unit according to any one of claims 1-4, characterized in that, include: Step 1. Periodically monitor the temperature and pressure at the outlet of each evaporator; Step 2. Control the flow direction of the regulating pump between adjacent flow paths according to the range of the difference in saturation temperature corresponding to the outlet pressure of adjacent evaporators, and automatically and evenly distribute the refrigerant flow rate between adjacent flow paths.

6. The uniform liquid separation control method as described in claim 5, characterized in that, Step 2 includes: Compare the saturation temperatures corresponding to the outlet pressures of the two evaporators on adjacent flow paths. The regulating pump opens from the flow path with the higher saturation temperature corresponding to the outlet pressure of the evaporator to the flow path with the lower saturation temperature corresponding to the outlet pressure of the evaporator, and the electronic expansion valve enters the automatic adjustment mode. When the absolute value of the difference between the saturation temperatures corresponding to the outlet pressures of adjacent evaporators is less than or equal to 1, the electronic expansion valve exits automatic adjustment, and the refrigeration unit enters fine-tuning mode.

7. The uniform liquid separation control method as described in claim 5, characterized in that, When the refrigeration unit is a dual-unit system, step 2 includes: When the difference between the saturation temperature Pc1 corresponding to the outlet pressure of the first evaporator and the saturation temperature Pc2 corresponding to the outlet pressure of the second evaporator is greater than 1, the regulating pump is turned on from the first flow path to the second flow path. When the difference between the saturation temperature Pc2 corresponding to the outlet pressure of the second evaporator and the saturation temperature Pc1 corresponding to the outlet pressure of the first evaporator is greater than 1, the regulating pump is turned on in the direction from the second flow path to the first flow path. When the absolute value of the difference between the saturation temperature Pc1 corresponding to the outlet pressure of the first evaporator and the saturation temperature Pc2 corresponding to the outlet pressure of the second evaporator is less than or equal to 1, the electronic expansion valve exits automatic adjustment and the refrigeration unit enters fine-tuning mode.

8. The uniform liquid separation control method as described in claim 7, characterized in that, When the regulating pump is turned on in the direction from the first flow path to the second flow path, the operating power of the regulating pump is controlled according to the following ratio: When the ratio of the difference between the saturation temperature corresponding to the outlet pressure of the first evaporator in the nth cycle and the saturation temperature corresponding to the outlet pressure of the second evaporator to the difference between the saturation temperature corresponding to the outlet pressure of the first evaporator in the previous cycle and the saturation temperature corresponding to the outlet pressure of the second evaporator in the previous cycle is greater than 1, the starting power of the regulating pump is A times the current power. When the ratio of the difference between the saturation temperature corresponding to the first evaporator outlet pressure in the nth cycle and the saturation temperature corresponding to the second evaporator outlet pressure to the difference between the saturation temperature corresponding to the first evaporator outlet pressure and the second evaporator outlet pressure in the previous cycle is equal to 1, the starting power W of the regulating pump remains unchanged. When the ratio of the difference between the saturation temperature corresponding to the first evaporator outlet pressure and the saturation temperature corresponding to the second evaporator outlet pressure in the nth cycle to the difference between the saturation temperature corresponding to the first evaporator outlet pressure and the saturation temperature corresponding to the second evaporator outlet pressure in the previous cycle is less than 1, the starting power of the regulating pump is B times the current power.

9. The uniform liquid separation control method as described in claim 7, characterized in that, When the regulating pump is turned on from the second flow path to the first flow path, the operating power of the regulating pump is controlled according to the following ratio: When the ratio of the difference between the saturation temperature corresponding to the outlet pressure of the second evaporator in the nth cycle and the saturation temperature corresponding to the outlet pressure of the first evaporator to the difference between the saturation temperature corresponding to the outlet pressure of the second evaporator and the saturation temperature corresponding to the outlet pressure of the first evaporator in the previous cycle is greater than 1, the starting power of the regulating pump is A times the current starting power. When the ratio of the difference between the saturation temperature corresponding to the outlet pressure of the second evaporator in the nth cycle and the saturation temperature corresponding to the outlet pressure of the first evaporator to the difference between the saturation temperature corresponding to the outlet pressure of the second evaporator in the previous cycle and the saturation temperature corresponding to the outlet pressure of the first evaporator in the previous cycle is equal to 1, the starting power W of the regulating pump remains unchanged. When the ratio of the difference between the saturation temperature corresponding to the outlet pressure of the second evaporator in the nth cycle and the saturation temperature corresponding to the outlet pressure of the first evaporator to the difference between the saturation temperature corresponding to the outlet pressure of the second evaporator in the previous cycle and the saturation temperature corresponding to the outlet pressure of the first evaporator is less than 1, the starting power of the regulating pump is B times the current power.

10. The uniform liquid separation control method as described in claim 8 or 9, characterized in that, The value of A is 0.95, and the value of B is 1.

03.

11. The uniform liquid separation control method as described in claim 7, characterized in that, The fine-tuning mode includes calculating the outlet superheat of each evaporator and adjusting the electronic expansion valve and regulating pump according to the range of outlet superheat.

12. The uniform liquid separation control method as described in claim 11, characterized in that... The fine-tuning modes include: If the outlet superheat of the first evaporator and the second evaporator satisfies: 7>T1≥T2>4 or 7>T2≥T1>4, the control mode of the refrigeration unit remains unchanged and the existing mode is maintained. If the outlet superheat of the first evaporator and the second evaporator meets the following condition: 7 > T1 ≥ 4 > T2, the opening degree B2 of the second electronic expansion valve is reduced by 1%, and the starting power W of the regulating pump remains unchanged. If the outlet superheat of the first evaporator and the second evaporator meets the condition: 7 > T2 ≥ 4 > T1, the opening degree B1 of the first electronic expansion valve is reduced by 1%, and the starting power W of the regulating pump remains unchanged. If the outlet superheat of the first evaporator and the second evaporator meets the following conditions: 4≥T1≥T2 or 4≥T2≥T1, the opening degree B1 of the first electronic expansion valve and the opening degree B2 of the second electronic expansion valve are reduced by 1%, and the starting power W of the regulating pump remains unchanged. If the outlet superheat of the first evaporator and the second evaporator meets the following conditions: T1≥T2≥10 or T2≥T1≥10, the opening degree B1 of the first electronic expansion valve and the opening degree B2 of the second electronic expansion valve are increased by 1%, and the starting power W of the regulating pump remains unchanged. If the outlet superheat of the first evaporator and the second evaporator meets the following conditions: T1≥10≥T2≥4, when the opening degree B1 of the first electronic expansion valve is increased by 1%, the starting power W of the regulating pump remains unchanged. If the outlet superheat of the first evaporator and the second evaporator meets the following condition: T2≥10≥T1≥4, the opening degree B2 of the second electronic expansion valve is increased by 1%, and the starting power W of the regulating pump remains unchanged. If the outlet superheat of the first evaporator and the second evaporator meets the following condition: T1≥10≥4≥T2, the opening degree B1 of the first electronic expansion valve is increased by 2%, the opening degree B2 of the second electronic expansion valve is decreased by 1%, and the regulating pump is turned on from the second flow path to the first flow path. At this time, it is determined whether the opening direction of the regulating pump is consistent with the original opening direction. If it is consistent, the opening power of the regulating pump is adjusted to 1.01 times the existing power; if it is inconsistent, the opening power of the regulating pump is adjusted to 0.05 times the total power of the regulating pump. If the outlet superheat of the first evaporator and the second evaporator meets the following condition: T2≥10≥4≥T1, the opening degree B2 of the second electronic expansion valve is increased by 2%, the opening degree B1 of the first electronic expansion valve is decreased by 1%, and the regulating pump is turned on from the first flow path to the second flow path. At this time, it is determined whether the opening direction of the regulating pump is consistent with the original opening direction. If it is consistent, the opening power of the regulating pump is adjusted to 1.01 times the current power. If it is inconsistent, the opening power of the regulating pump is adjusted to 0.05 times the total power of the regulating pump. T1 is the outlet superheat of the first evaporator, and T2 is the outlet superheat of the second evaporator.

13. The uniform liquid separation control method as described in claim 6, characterized in that, The automatic adjustment opening B of the electronic expansion valve is: the current opening B. N The sum of the adjustment steps Sn1 in the nth period and Sn2 in the (n-1)th period, B = B N +Sn1+S12, where: Sn1=(T1 n -5.5);Sn2=S1*[(T1 n -5.5) / (T1 n-1 -5.5)-1]; In the above formula: T1 n It is the outlet superheat of the nth period, T1 n-1 Export overheating in the (n-1)th cycle.

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