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

Abstract

The invention discloses a multi-split refrigerating unit and a uniform liquid separation control method thereof. The control method comprises the following steps: detecting the temperature and the pressure of an outlet of each evaporator according to a period; the flow direction of the adjusting pump between the adjacent flow paths is controlled according to the range of the difference value of the saturation temperature corresponding to the outlet pressure of the adjacent evaporators, and the flow of refrigerants on the adjacent flow paths is automatically distributed in a balanced mode. According to the difference of the saturation temperatures corresponding to the outlet pressures of the evaporators on the adjacent flow paths and the range of the outlet superheat degree, the flow of refrigerants in the two pipes is automatically and evenly distributed through the adjusting pump, it is guaranteed that liquid distribution is even under various working conditions, and the running reliability of a unit is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioning, and in particular to a one-to-many refrigeration unit and a control method for uniform liquid distribution thereof. Background Art

[0002] In a multi-split system, one host is usually used to provide cooling for multiple terminals, typically a one-to-two refrigeration unit. In a multi-split system, the liquid separation device is the key part to achieve on-demand distribution of refrigerant between multiple indoor units (or cold storage). The liquid separation device usually includes components such as a liquid separator and an electronic expansion valve, which are used to control the refrigerant flow entering each indoor unit. The liquid separator uses the principles of gravity and inertia to achieve gas-liquid separation to ensure 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 liquid separator, a liquid separation pipe is usually used to guide the liquid separation process. Due to the different pipeline lengths and operating environments of each indoor unit, it is easy to cause uneven liquid separation of the unit. Increasing the length of the liquid separation pipe within a certain range can significantly improve the uniformity of refrigerant distribution between multiple evaporators or indoor units. This is because the increase in the length of the liquid separation pipe helps to reduce the flow resistance and pressure loss of the refrigerant in the pipeline, so that the refrigerant can be distributed more smoothly to each evaporator or indoor unit. As the length of the liquid separation pipe increases, the flow deviation will gradually decrease. When the length of the distributor pipe is long enough, the flow of refrigerant in the pipeline is more stable, thereby reducing flow deviation. However, when the length of the distributor pipe increases to a certain extent, its improvement effect on flow deviation will gradually slow down. This is because the flow resistance in the pipeline is relatively small at this time, and the effect of increasing the length of the distributor pipe on flow distribution is no longer significant. In fact, the length of the distributor pipe is also limited by the installation site. In engineering, the length of the distributor pipe is usually adjusted under certain working conditions, and then adjusted by the electronic expansion valve when the unit is running. However, under extreme conditions, the adjustment of the electronic expansion valve is relatively uneven, which can easily lead to excessive distributor in a certain indoor unit, severe frosting, lower pressure on the low-pressure side, loss of compressor life, and reduced unit reliability. Summary of the invention

[0003] The present invention provides a one-to-many refrigeration unit and a control method for uniform liquid distribution thereof, so as to solve the technical problem of uneven liquid distribution in internal units existing in the prior art, so as to ensure the reliability of the operation of the one-to-many refrigeration unit.

[0004] The technical solution adopted by the present invention is to propose a one-to-many refrigeration unit, including N flow paths branching out from the condenser outlet pipe leading to the terminal device, each flow path is provided with an electronic expansion valve and an evaporator, the outlet pipes of each evaporator converge and are connected to the compressor suction pipe of the refrigeration unit, wherein 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 regulating pump to balance the flow to each evaporator according to the difference in saturation temperature corresponding to the evaporator outlet pressure on adjacent flow paths and the outlet superheat.

[0005] In one embodiment, the one-to-many refrigeration unit includes two flow paths, a branch is provided between the inlet sections of the first flow path and the second flow path, and a regulating pump is provided on the branch.

[0006] In another embodiment, the one-to-many refrigeration unit includes four flow paths, a branch is provided between the first flow path and the second flow path, a branch is provided between the second flow path and the third flow path, and a branch is provided between the third flow path and the fourth flow path, and a regulating pump is provided on each branch.

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

[0008] The present invention also provides a uniform liquid distribution control method for a one-to-many refrigeration unit, comprising:

[0009] Step 1. Periodically detect the temperature and pressure at the outlet of each evaporator;

[0010] Step 2. Control the flow direction of the regulating pumps between adjacent flow paths according to the range of the difference in saturation temperature corresponding to the outlet pressures of adjacent evaporators, and automatically and evenly distribute the flow of the refrigerant on the adjacent flow paths.

[0011] Furthermore, the step 2 comprises:

[0012] Compare the saturation temperatures corresponding to the outlet pressures of two evaporators on adjacent flow paths, adjust the pump to open from the flow path with a larger saturation temperature corresponding to the outlet pressure of the evaporator to the flow path with a smaller saturation temperature corresponding to the outlet pressure of the evaporator, and the electronic expansion valve enters the automatic adjustment mode;

[0013] 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.

[0014] In a one-to-two refrigeration unit, step 2 includes:

[0015] 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 regulating pump is turned on in the direction from the first flow path to the second flow path;

[0016] 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 regulating pump is turned on in the direction from the second flow path to the first flow path;

[0017] 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.

[0018] Furthermore, 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:

[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 previous cycle is greater than 1, (Pc1 n -Pc2 n ) / (Pc1 n-1 -Pc2 n-1 )>1, adjust the pump start power to 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 and 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 equal to 1, (Pc1 n -Pc2 n ) / (Pc1 n-1 -Pc2 n-1 )=1, the opening power W of the regulating pump remains 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 previous cycle is less than 1, (Pc1 n -Pc2 n ) / (Pc1 n-1-Pc2 n-1 )<1, adjust the pump's start-up power to B times the current power.

[0022] Further, when the regulating pump is turned on in the direction 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 ratio of the difference between the saturation temperature corresponding to the second evaporator outlet pressure in the nth cycle and the saturation temperature corresponding to the first evaporator outlet pressure to the difference between the saturation temperature corresponding to the second evaporator outlet pressure in the previous cycle and the saturation temperature corresponding to the first evaporator outlet pressure is greater than 1, (Pc2 n -Pc1 n ) / (Pc2 n-1 -Pc1 n-1 )>1, adjust the pump start-up power to A times the current start-up power;

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

[0025] When the ratio of the difference between the saturation temperature corresponding to the second evaporator outlet pressure in the nth cycle and the saturation temperature corresponding to the first evaporator outlet pressure to the difference between the saturation temperature corresponding to the second evaporator outlet pressure in the previous cycle and the saturation temperature corresponding to the first evaporator outlet pressure is less than 1, (Pc2 n -Pc1 n ) / (Pc2 n-1 -Pc1 n-1 )<1, adjust the pump's start-up power to B times the current power.

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

[0027] Furthermore, the fine-tuning mode includes 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-tuning mode includes:

[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 refrigeration unit remains unchanged and the existing operation mode is maintained;

[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 remains unchanged;

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

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

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

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

[0036] If the outlet superheat of the first evaporator and the second evaporator satisfies: T1≥10≥4≥T2, the opening B1 of the first electronic expansion valve is increased by 2%, the opening 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 flow 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;

[0037] If the outlet superheat of the first evaporator and the second evaporator satisfies: T2≥10≥4≥T1, the opening B2 of the second electronic expansion valve is increased by 2%, the opening 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 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 the current power. If inconsistent, the opening power of the regulating pump is adjusted to 0.05 times the total power of the regulating pump.

[0038] Furthermore, the automatic adjustment opening degree B of the electronic expansion valve is: the current opening degree B N, the sum of the number of adjustment steps Sn1 in the nth cycle and the number of adjustment steps Sn2 in the n-1th cycle, 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 is the outlet superheat of the nth cycle, T1 n-1 Outlet superheat of cycle n-1.

[0041] Compared with the prior art, the technical solution proposed by the present invention has the following beneficial effects:

[0042] The present invention adds a branch between adjacent flow paths, and adds a regulating pump on the branch to balance the flow of evaporators on adjacent flow paths through the regulating pump, thereby improving liquid separation uniformity and refrigeration efficiency.

[0043] The liquid equalization control method proposed in the present invention automatically detects parameters such as the outlet temperature and outlet pressure of each evaporator, and automatically and evenly distributes the flow of refrigerant in the two pipes through an adjusting pump according to the difference in saturation temperatures corresponding to the outlet pressures of the evaporators on adjacent flow paths and the range of outlet superheat, thereby ensuring uniform liquid distribution under various working conditions, maintaining relatively consistent states of the one-to-many internal units, and ensuring the reliability of the unit operation. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0049] Figure 5 is a schematic block diagram of the liquid uniformity control method proposed by the present invention;

[0050] Figure 6 yes Figure 1 A flow chart of regulating the pump in the embodiment shown;

[0051] Figure 7 yes Figure 1 A flow chart showing the refrigeration unit entering a fine adjustment mode in the illustrated embodiment.

[0052] in:

[0053] 1 compressor, 2 condenser, 3 gas-liquid separator, 4 branch, 5 regulating pump, 6 air 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 adjusts the opening;

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

[0056] B1: Current opening of the first electronic expansion valve;

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

[0058] W adjusts the opening power of the pump;

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

[0060] Wz regulates the total power of the 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 first evaporator outlet superheat;

[0068] T2 second evaporator outlet superheat;

[0069] nDetection cycle;

[0070] The number of adjustment steps for the electronic expansion in the nth period of Sn1;

[0071] The number of adjustment steps for the electronic expansion of Sn2 in the n-1th period. DETAILED DESCRIPTION

[0072] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention is described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the following specific embodiments are only used to explain the present invention and do not constitute a limitation to the present invention.

[0073] The terms used in this specification are only for describing specific embodiments and are not intended to limit the present invention. Unless otherwise specifically stated, the relative arrangement of the components and steps, numerical expressions and numerical values ​​described in these embodiments do not limit the protection scope of the present invention.

[0074] The techniques, methods and equipment known to ordinary technicians in the relevant fields are not discussed in detail in this specification, but where appropriate, the techniques, methods and equipment should be considered as part of this specification. Any specific values ​​in this specification should be interpreted as being merely exemplary and not limiting the present invention.

[0075] For the convenience of description, the terms describing the position used in the specification, such as "above...", "to the left of...", "in front of...", etc., are only used to describe the spatial position relationship between a certain component and other components of the embodiment shown in the figure. When the position of the component is different, the relative position will change. Therefore, the position relationship of the embodiment of the drawing should not constitute a limitation to the present invention.

[0076] In addition, it should be noted that the terms "first" and "second" used in the specification are only used to distinguish similar components, and there is no order of precedence, so they cannot be understood as limiting the scope of protection of the present invention.

[0077] The concept of the present invention is to add a branch between adjacent flow paths leading to the evaporator, and to set a regulating pump on the branch to balance the flow to each evaporator by adjusting the flow direction and power of the regulating pump.

[0078] The existing one-to-many refrigeration unit includes N flow paths branching from the condenser outlet pipe leading to the terminal device, each flow path is provided with an electronic expansion valve and an evaporator, and the outlet pipes of each evaporator converge and communicate with the compressor suction pipe of the refrigeration unit. The improvement of the present invention is to set a branch between adjacent flow paths, and set a regulating pump on the branch. The controller of the refrigeration unit controls the flow direction and power of the regulating pump according to the difference in saturation temperature corresponding to the outlet pressure of the evaporators on the 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 proposed in the present invention is shown, and the one-to-two refrigeration unit consists of an outdoor unit and an indoor unit. The outdoor unit includes: a compressor 1, a condenser 2 and a gas-liquid separator 3. The indoor unit includes two flow paths branched from the refrigerant outlet pipe of the condenser, a first flow path 10 and a second flow path 20, and the first flow path is provided with a first electronic expansion valve 11 and a first evaporator 12; 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 an air intake stop valve 6 and a liquid supply stop valve 7. The first evaporator and the second evaporator provide cooling to the room, and then the first flow path and the second flow path merge and are connected to the air intake pipe of the compressor.

[0080] In the refrigeration cycle, the refrigerant is compressed by the compressor 1 to become a high-temperature and high-pressure gas, and then releases heat and liquefies in the condenser 2 to become a high-pressure and room-temperature liquid. It is then divided into two paths. The refrigerant in the first path is throttled by the first electronic expansion valve 11 and flows to the first evaporator 12 for cooling; the refrigerant in the second path is throttled by the second electronic expansion valve 21 and flows to the second evaporator 22 for cooling. The refrigerant evaporates and absorbs heat in the first evaporator and the second evaporator, and then merges and returns to the compressor cycle.

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

[0082] In order to ensure uniform liquid separation between the first evaporator and the second evaporator in a one-to-two refrigeration unit, the refrigeration unit proposed in the present invention is provided with a branch 4 between the inlet pipes of the first flow path 10 and the second flow path 20, and a regulating pump 5 is provided on the branch. The controller of the refrigeration unit automatically detects parameters such as the outlet temperature and outlet pressure of each evaporator after liquid separation, and automatically and evenly distributes the flow rate of the refrigerant on the first flow path and the second flow path according to the difference in saturation temperature corresponding to the outlet pressures of adjacent evaporators and the range of outlet superheat through the regulating pump, thereby ensuring uniform liquid separation under various working conditions, maintaining relatively consistent states of the one-to-two indoor heat exchangers, and ensuring the reliability of the unit operation.

[0083] Assume that the current opening of the first electronic expansion valve 11 is B1, the current opening of the second electronic expansion valve 21 is B2, the initial opening of the first electronic expansion valve and the second electronic expansion valve is determined according to the external environment and the internal environment (conventional technical means), the total power of the regulating 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 during actual operation.

[0084] like Figure 5 As shown, the uniform liquid distribution control method of a one-to-many refrigeration unit proposed by the present invention includes:

[0085] Step 1. Periodically detect the temperature and pressure at the outlet of each evaporator;

[0086] Step 2. Control the flow direction and power of the regulating pumps between adjacent flow paths according to the range of the difference in saturation temperature corresponding to the outlet pressures of adjacent evaporators, and automatically and evenly distribute the flow of the refrigerant on the adjacent flow paths.

[0087] The step 2 comprises:

[0088] Compare the saturation temperatures corresponding to the outlet pressures of two evaporators on adjacent flow paths, and adjust the pump to open from the flow path with a higher saturation temperature corresponding to the outlet pressure of the evaporator to the flow path with a lower saturation temperature corresponding to the outlet pressure of the evaporator;

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

[0090] Figure 6 A flow chart showing a control method for uniform liquid distribution of a regulating pump of a one-to-two refrigeration unit, including the following steps:

[0091] Firstly, the outlet temperature and pressure of the first evaporator and the second evaporator are detected, and the outlet superheat is calculated;

[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 converted according to the outlet pressure P1, and the outlet superheat T1=Tc1-Pc1 of the first evaporator is calculated; the outlet temperature Tc2 and outlet pressure P2 of the second evaporator 22 are measured, the corresponding saturation temperature Pc2 is converted according to the outlet pressure P2, and the outlet superheat T2=Tc2-Pc2 of the second evaporator is calculated.

[0093] Then, 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, the flow direction of the pump 5 on the branch is controlled to automatically and evenly distribute the flow of the refrigerant on the first flow path and the second flow path, and the adjustment is divided into three situations:

[0094] 1. 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 regulation. At this time, the regulating pump 5 is turned on from the first flow path 10 to the second flow path 20 (such as Figure 2 The pump direction remains unchanged for subsequent adjustments until this adjustment is completed.

[0095] The operating power of the pump is then controlled and adjusted according to the following ratio:

[0096] When 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 saturation temperature Pc1n corresponding to the outlet pressure of the first evaporator in the previous cycle, n-1 Saturation temperature Pc2 corresponding to the outlet pressure of the second evaporator n-1 When the ratio of the difference is greater than 1, (Pc1n-Pc2n) / (Pc1n-1-Pc2n-1)>1, the start-up power of the adjustment pump 5 is A times the current power, and the value of A in this embodiment is 0.95;

[0097] When 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 saturation temperature Pc1n corresponding to the outlet pressure of the first evaporator in the previous cycle, n-1 Saturation temperature Pc2 corresponding to the outlet pressure of the second evaporator n-1 When the ratio of the difference is equal to 1, (Pc1n-Pc2n) / (Pc1n-1-Pc2n-1)=1, the start-up power of the adjustment pump 5 is maintained to maintain the current start-up power W unchanged;

[0098] When 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 saturation temperature Pc1n corresponding to the outlet pressure of the first evaporator in the previous cycle, n-1 Saturation temperature Pc2 corresponding to the outlet pressure of the second evaporator n-1 When the ratio of the difference is less than 1, (Pc1n-Pc2n) / (Pc1n-1-Pc2n-1)<1, the start-up power of the adjustment 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 regulation, and the regulating pump 5 is turned on from the second flow path 20 to the first flow path 10 (such as Figure 3 The pump direction will not be changed in subsequent adjustments until this adjustment is completed.

[0100] The operating power of the pump is then controlled and adjusted according to the following ratio:

[0101] When 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 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 difference is greater than 1, (Pc2n-Pc1n) / (Pc2 n-1 -Pc1 n-1 )>1, the start-up power of the adjustment pump 5 is A times of the current start-up power, and the value of A in this embodiment is 0.95;

[0102] When 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 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 difference is equal to 1, (Pc2n-Pc1n) / (Pc2n-1-Pc1n-1)=1, the start-up power of the adjustment pump 5 is maintained to maintain the current start-up power W unchanged;

[0103] When 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 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 difference is less than 1, (Pc2n-Pc1n) / (Pc2n-1-Pc1n-1)<1, the start-up power of the adjustment pump 5 is 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 regulating pump according to the relationship between the outlet superheat T1 of the first evaporator and the outlet superheat T2 of the second evaporator, and specifically includes nine operating modes:

[0106] If 7>T1≥T2>4 or 7>T2≥T1>4, the control mode of the refrigeration unit remains unchanged and the existing operation 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 opening 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 remains 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 remains 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 remains 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 remains unchanged;

[0113] If T1≥10≥4≥T2, the opening B1 of the first electronic expansion valve 11 is increased by 2%, the opening B2 of the second electronic expansion valve 21 is decreased by 1%, and the regulating pump 5 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 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 turned off or the direction is 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 decreased by 1%, and the regulating pump 5 is turned on from the first flow path to the second flow path. At this time, it is determined whether the opening flow direction of the regulating pump is consistent with the original opening direction. If the regulating pump flow path is consistent with the original regulating pump opening direction, 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 turned off or the direction is 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-tuning is completed, exit and press again in the next cycle. Figure 6 Control the process.

[0116] Automatic adjustment of electronic expansion valve: The automatic adjustment opening B of the electronic expansion valve on a certain flow path is the current opening B of the flow path. N , the sum of the number of adjustment steps Sn1 in the nth cycle and the number of adjustment steps Sn2 in the n-1th cycle, B = BN + Sn1 + S12, where: 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 outlet superheat of the nth cycle, T1 n-1 Outlet superheat of cycle n-1.

[0119] Taking the first flow path 10 as an example, the automatic adjustment opening B of the first electronic expansion valve 11 is: the sum of the current opening B1, the adjustment step number B11 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-1th cycle, B=B1+S11+S12, where:

[0120] B1 is the current opening degree of the first electronic expansion valve;

[0121] S11 is the number of adjustment steps of the first electronic expansion valve in the nth cycle, S12 is the number of adjustment steps of the first electronic expansion valve in the n-1th cycle, and S11 and S12 vary according to the detection 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 on the first flow path in the nth cycle, T1 n-1 It is the evaporator outlet superheat on the first flow path in the n-1th cycle.

[0124] The automatic adjustment opening of the second electronic expansion valve 22 is the same as that of the first electronic expansion valve, which is equal to B2+S21+S22, where 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-1th cycle.

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

[0126] Figure 4It is a system diagram of another embodiment of the present invention. This embodiment is a one-to-four refrigeration unit, including four flow paths branching from the condenser outlet pipe leading 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 pipes of each evaporator converge and are connected to the compressor suction pipe of the refrigeration unit. A branch 4 is provided between each adjacent flow path, and a regulating pump 5 is provided on the branch. The controller of the refrigeration unit controls each regulating pump to balance the flow to each evaporator according to the difference in saturation temperature corresponding to the outlet pressure of the evaporators on adjacent flow paths and the mutual relationship of the outlet superheat of the evaporators.

[0127] In the case of one-to-many pumps, the control of the regulating pumps is based on the adjacent flow paths as a control unit, that is, Figure 4 The first flow path 10 and the second flow path 20 are a 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, and branches and regulating pumps are provided between adjacent flow paths. In this embodiment, three regulating pumps 5 are provided, each regulating pump is a control unit, and each control unit is independently controlled without affecting each other. The electronic expansion valve on each flow path is controlled according to its own situation.

[0128] If multiple adjustment 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 pump flow direction is adjusted from the second flow path 20 to the first flow path 10, and the second flow path 20 and the third flow path 30 enter the automatic adjustment mode, and the pump flow direction is adjusted from the third flow path 30 to the second flow path 20, or the pump is adjusted from the first flow path 10 to the second flow path 20, and the third flow path 30 to the second flow path 20. After entering the automatic adjustment, the direction of the adjustment pump remains unchanged, and the power of the adjustment pump is only adjusted according to the size of (Pc1 n-Pc2n) / (Pc1 n-1-Pc2n-1) until this adjustment is completed.

[0129] The liquid equalization control method proposed in the present invention automatically detects parameters such as the outlet temperature and outlet pressure of each evaporator, and automatically and evenly distributes the flow of refrigerant in the two pipes through an adjusting pump according to the difference in saturation temperatures corresponding to the outlet pressures of the evaporators on adjacent flow paths and the range of outlet superheat, thereby ensuring uniform liquid distribution under various working conditions, maintaining relatively consistent states of the one-to-many internal units, and ensuring the reliability of the unit operation.

[0130] The above description is only a specific implementation of the present invention. It should be pointed out that any modification, equivalent substitution and change made within the spirit and framework of the present invention should be included in the protection scope of the present invention.

Claims

1. A one-to-many refrigeration unit, comprising N flow paths branching from the condenser outlet pipe to the terminal device, each flow path is provided with an electronic expansion valve and an evaporator, the outlet pipes of each evaporator converge and communicate with 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 regulating pump to balance the flow to each evaporator according to the difference in saturation temperature corresponding to the evaporator outlet pressure on adjacent flow paths and the outlet superheat.

2. The one-to-many refrigeration unit according to claim 1, characterized in that: The invention comprises two flow paths, a branch path is arranged between the inlet sections of the first flow path and the second flow path, and a regulating pump is arranged on the branch path.

3. The one-to-many refrigeration unit according to claim 1, characterized in that: It comprises four flow paths, a branch is arranged between the first flow path and the second flow path, a branch is arranged between the second flow path and the third flow path, a branch is arranged between the third flow path and the fourth flow path, and each branch is arranged with a regulating pump.

4. The one-to-many refrigeration unit according to claim 2 or 3, characterized in that: The outlet end of the evaporator is provided with a temperature sensor and a pressure sensor.

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

6. The uniform liquid separation control method according to claim 5, characterized in that: The step 2 comprises: Compare the saturation temperatures corresponding to the outlet pressures of two evaporators on adjacent flow paths, adjust the pump to open from the flow path with a larger saturation temperature corresponding to the outlet pressure of the evaporator to the flow path with a smaller 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 according to claim 5, characterized in that: When the refrigeration unit is one-to-two, 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 in the direction 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 first evaporator outlet pressure and the saturation temperature Pc2 corresponding to the second evaporator outlet pressure 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 according to 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 first evaporator outlet pressure and the saturation temperature corresponding to the second evaporator outlet pressure in the nth cycle and 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 greater than 1, the opening 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 and the saturation temperature corresponding to the second evaporator outlet pressure in the nth cycle and 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 equal to 1, the opening 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 start-up power of the regulating pump is B times the current power.

9. The uniform liquid separation control method according to claim 7, characterized in that: When the regulating pump is turned on in the direction 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 second evaporator outlet pressure and the saturation temperature corresponding to the first evaporator outlet pressure in the nth cycle and the difference between the saturation temperature corresponding to the second evaporator outlet pressure and the saturation temperature corresponding to the first evaporator outlet pressure in the previous cycle is greater than 1, the opening power of the regulating pump is A times the current opening power; When the ratio of the difference between the saturation temperature corresponding to the second evaporator outlet pressure and the saturation temperature corresponding to the first evaporator outlet pressure in the nth cycle and the difference between the saturation temperature corresponding to the second evaporator outlet pressure and the saturation temperature corresponding to the first evaporator outlet pressure in the previous cycle is equal to 1, the opening power W of the regulating pump remains unchanged; When the ratio of the difference between the saturation temperature corresponding to the second evaporator outlet pressure in the nth cycle and the saturation temperature corresponding to the first evaporator outlet pressure to the difference between the saturation temperature corresponding to the second evaporator outlet pressure in the previous cycle and the saturation temperature corresponding to the first evaporator outlet pressure is less than 1, the start-up power of the regulating pump is B times the current power.

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

03.

11. The uniform liquid separation control method according to claim 7, characterized in that: The fine-tuning mode includes 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.

12. The uniform liquid separation control method according to claim 11, characterized in that The fine-tuning mode includes: 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 operation mode is maintained; 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 remains unchanged; If the outlet superheat of the first evaporator and the second evaporator satisfies: 7>T2≥4>T1, the opening B1 of the first electronic expansion valve is reduced by 1%, and the opening power W of the regulating pump remains unchanged; If the outlet superheat of the first evaporator and the second evaporator satisfies: 4≥T1≥T2 or 4≥T2≥T1, the opening B1 of the first electronic expansion valve and the opening B2 of the second electronic expansion valve are reduced by 1%, and the opening power W of the regulating pump remains unchanged; If the outlet superheat of the first evaporator and the second evaporator satisfies: T1≥T2≥10 or T2≥T1≥10, the opening B1 of the first electronic expansion valve and the opening B2 of the second electronic expansion valve are increased by 1%, and the opening power W of the regulating pump remains unchanged; If the outlet superheat of the first evaporator and the second evaporator satisfies: T1≥10≥T2≥4, when the opening degree B1 of the first electronic expansion valve is increased by 1%, the opening power W of the regulating pump remains unchanged; 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 remains unchanged; If the outlet superheat of the first evaporator and the second evaporator satisfies: T1≥10≥4≥T2, the opening B1 of the first electronic expansion valve is increased by 2%, the opening 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 flow 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 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 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 flow 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; In the above, 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 according to claim 6, characterized in that: The automatic adjustment opening degree B of the electronic expansion valve is: the current opening degree B N , the sum of the number of adjustment steps Sn1 in the nth cycle and the number of adjustment steps Sn2 in the n-1th cycle, 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 is the outlet superheat of the nth cycle, T1 n-1 Outlet superheat of cycle n-1.

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