Refrigerant pump multi-connected system capable of preventing cavitation

Abstract

The utility model relates to the technical field of air conditioners, in particular to an anti-cavitation refrigerant pump multi-connected system which comprises an outdoor unit, an indoor unit, a main liquid pipe and a main air pipe. The outdoor unit comprises a heat exchanger, a liquid storage device and a refrigerant pump. The heat exchanger comprises a first heat exchange channel; one end of the first heat exchange channel is communicated with the main air pipe; the other end of the first heat exchange channel is communicated with one end of the liquid storage device; the other end of the liquid storage device is communicated with inlets of all the refrigerant pumps; and the main liquid pipe is communicated with outlets of all the refrigerant pumps. By arranging the first bypass branch, the first switch valve, the second bypass branch and the second switch valve, the risk of pump cavitation caused by insufficient liquid refrigerant at the inlet of the refrigerant pump can be prevented, and the risk of pump cavitation caused by easy vaporization of the inlet of the refrigerant pump due to insufficient supercooling degree can be prevented.

Description

Technical Field

[0001] The utility model relates to the technical field of air conditioning, in particular to a refrigerant pump multi-connection system for preventing cavitation. Background Art

[0002] In a multi-connected fluorine pump system, there are multiple evaporator terminals, and the cooling requirements of each terminal are different. Especially when the cooling requirements of some terminals are small, a large amount of liquid refrigerant will remain in different evaporators, which will lead to lack of liquid at the fluorine pump inlet and cause cavitation and idling. To solve this problem, two methods are usually used:

[0003] The first method is to add a liquid accumulator: adding a liquid accumulator at the fluorine pump inlet to ensure that there is always an adequate supply of liquid refrigerant at the fluorine pump inlet. However, even with the addition of a liquid accumulator, due to the presence of saturated refrigerant in the liquid accumulator, the saturated refrigerant in the section of the pipeline from the liquid accumulator to the centrifugal fluorine pump will easily vaporize due to pipeline resistance if the pressure changes, thus causing cavitation in the centrifugal pump.

[0004] The first method is to pre-cool the pipeline: adding a heat exchanger to further pre-cool the pipeline at the fluorine pump inlet to reduce the refrigerant temperature and reduce the possibility of vaporization. However, this method also has certain limitations. For example, adding a heat exchanger increases system complexity and cost, and the increase in pipeline connection points also leads to reduced system reliability. Utility Model Content

[0005] The purpose of the utility model is to provide a refrigerant pump multi-connection system for preventing cavitation in view of the above-mentioned deficiencies in the prior art.

[0006] The purpose of the utility model is achieved through the following technical solutions: a refrigerant pump multi-connected system for preventing cavitation, comprising an outdoor unit, an indoor unit, a main liquid pipe and a main gas pipe;

[0007] The outdoor unit includes a heat exchanger, a liquid accumulator, and a plurality of refrigerant pumps connected in parallel; the heat exchanger includes a first heat exchange channel; one end of the first heat exchange channel is connected to the main gas pipe; the other end of the first heat exchange channel is connected to one end of the liquid accumulator; the other end of the liquid accumulator is connected to the inlets of all refrigerant pumps; the main liquid pipe is connected to the outlets of all refrigerant pumps;

[0008] A first bypass branch is provided between one end of the first heat exchange channel and the outlets of all refrigerant pumps; the first bypass branch is provided with a first switch valve;

[0009] A second bypass branch is provided between the other end of the first heat exchange channel and the inlets of all refrigerant pumps; and a second switch valve is provided on the second bypass branch.

[0010] The present invention is further configured such that a first temperature sensor is provided at one end of the first heat exchange channel; a second temperature sensor and a first pressure sensor are provided at the inlet of the refrigerant pump; and a second pressure sensor is provided at the outlet of the refrigerant pump.

[0011] The utility model is further configured such that the heat exchanger is provided with a second heat exchange channel; one end of the second heat exchange channel is connected to a water outlet pipe; the other end of the second heat exchange channel is connected to a water inlet pipe;

[0012] The water inlet pipe or the water outlet pipe is provided with a water valve.

[0013] The present invention is further configured such that a third temperature sensor and a third pressure sensor are provided at one end of the second heat exchange channel; and a fourth temperature sensor and a fourth pressure sensor are provided at the other end of the second heat exchange channel.

[0014] The utility model is further configured such that the outlet of each refrigerant pump is connected to a one-way valve; the outlet of each refrigerant pump is communicated with the first bypass branch and the main liquid pipe after passing through the one-way valve.

[0015] The utility model is further configured such that the multi-connected refrigerant pump system for preventing cavitation includes a plurality of indoor units; the plurality of indoor units are arranged in parallel between the main liquid pipe and the main gas pipe.

[0016] The present invention is further configured such that the indoor unit includes an evaporator, an air distribution pipe provided between one end of the evaporator and the main air pipe, and a liquid distribution pipe provided between the other end of the evaporator and the main liquid pipe.

[0017] The present invention is further configured such that the liquid dispensing pipe is provided with an electronic expansion valve.

[0018] The present invention is further configured such that the gas distribution pipe is provided with a fifth temperature sensor and a fifth pressure sensor; and the liquid distribution pipe is provided with a sixth temperature sensor.

[0019] The utility model is further configured such that the gas distribution pipe is provided with a first control valve; the liquid distribution pipe is provided with a second control valve; a third control valve is provided between the other end of the first heat exchange channel and the liquid reservoir; and a fourth control valve is provided between the main liquid pipe and the refrigerant pump.

[0020] The beneficial effects of the present invention are as follows: by setting a first bypass branch and a first switch valve, as well as a second bypass branch and a second switch valve, the present invention can prevent the risk of pump cavitation caused by insufficient liquid refrigerant at the refrigerant pump inlet and prevent the risk of pump cavitation caused by easy vaporization of the refrigerant pump inlet due to insufficient supercooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The utility model is further described using the accompanying drawings, but the embodiments in the accompanying drawings do not constitute any limitation to the utility model. A person skilled in the art can obtain other drawings based on the following drawings without making any creative effort.

[0022] Figure 1 It is a system principle diagram of the utility model;

[0023] Among them: 11, outdoor unit; 12, indoor unit; 13, main liquid pipe; 14, main gas pipe; 15, fourth control valve; 2, heat exchanger; 21, first heat exchange channel; 22, second heat exchange channel; 23, liquid reservoir; 24, third control valve; 31, water inlet pipe; 32, water outlet pipe; 33, water valve; 4, refrigerant pump; 41, one-way valve; 51, first bypass branch; 52, first on-off valve; 61, second bypass branch; 62, second on-off valve; 71, first temperature control valve sensor; 72, second temperature sensor; 73, third temperature sensor; 74, fourth temperature sensor; 75, fifth temperature sensor; 76, sixth temperature sensor; 81, first pressure sensor; 82, second pressure sensor; 83, third pressure sensor; 84, fourth pressure sensor; 85, fifth pressure sensor; 91, evaporator; 92, gas distribution pipe; 93, liquid distribution pipe; 94, electronic expansion valve; 95, first control valve; 96, second control valve. DETAILED DESCRIPTION

[0024] The present invention will be further described with reference to the following embodiments.

[0025] Depend on Figure 1 It can be seen that the refrigerant pump multi-connected system for preventing cavitation described in this embodiment includes an outdoor unit 11, an indoor unit 12, a main liquid pipe 13 and a main gas pipe 14;

[0026] The outdoor unit 11 includes a heat exchanger 2, a liquid accumulator 23, and several refrigerant pumps 4 connected in parallel. The heat exchanger 2 includes a first heat exchange channel 21. One end of the first heat exchange channel 21 is connected to the main air pipe 14. The other end of the first heat exchange channel 21 is connected to one end of the liquid accumulator 23. The other end of the liquid accumulator 23 is connected to the inlets of all refrigerant pumps 4. The main liquid pipe 13 is connected to the outlets of all refrigerant pumps 4. The heat exchanger 2 is a plate heat exchanger.

[0027] A first bypass branch 51 is provided between one end of the first heat exchange channel 21 and the outlets of all refrigerant pumps 4; the first bypass branch 51 is provided with a first switch valve 52;

[0028] A second bypass branch 61 is provided between the other end of the first heat exchange channel 21 and the inlet of all refrigerant pumps 4 ; a second switch valve 62 is provided in the second bypass branch 61 ; both the first switch valve 52 and the second switch valve 62 are solenoid valves.

[0029] Specifically, the refrigerant pump multi-connected system for preventing cavitation described in this embodiment, by setting a first bypass branch 51 and a first switch valve 52, can allow a portion of the liquid refrigerant at the outlet of the refrigerant pump 4 to enter one end of the heat exchanger 2 through the first bypass branch 51 by opening the first switch valve 52, thereby replenishing the liquid refrigerant in the liquid reservoir 23, thereby preventing the risk of pump cavitation due to insufficient liquid refrigerant at the inlet of the refrigerant pump 4, or the risk of flow interruption due to insufficient pressure difference before and after the pump.

[0030] In addition, by setting up a second bypass branch 61 and a second switch valve 62, by opening the second switch valve 62, the refrigerant at the other end of the heat exchanger 2 obtains a subcooled refrigerant, which can directly enter the inlet of the refrigerant pump 4 through the second bypass branch 61, which can effectively prevent the risk of pump cavitation caused by easy vaporization due to insufficient subcooling at the inlet of the refrigerant pump 4, or the risk of failing to establish an effective lift due to insufficient pressure difference before and after the pump.

[0031] In the multi-connected refrigerant pump system for preventing cavitation described in this embodiment, a first temperature sensor 71 is provided at one end of the first heat exchange channel 21; a second temperature sensor 72 and a first pressure sensor 81 are provided at the inlet of the refrigerant pump 4; and a second pressure sensor 82 is provided at the outlet of the refrigerant pump 4.

[0032] Specifically, the first control logic of this embodiment is: the second switch valve 62 remains normally closed;

[0033] When it is detected for a first continuous duration (settable, 10s by default) that the subcooling degree at the inlet of the refrigerant pump 4 is less than a subcooling degree opening setting value (settable, 1° C. by default), the second switch valve 62 is opened.

[0034] When the pressure difference before and after the refrigerant pump 4 is detected to be less than the pump cut-off pressure difference (settable, default 0.5 bar) for a first continuous duration (settable, default 10 seconds), the second switch valve 62 is opened.

[0035] By setting up the first bypass branch 51 and the first switch valve 52, and by opening the first switch valve 52, a part of the liquid refrigerant at the outlet of the refrigerant pump 4 can enter one end of the heat exchanger 2 through the first bypass branch 51, so as to replenish the liquid refrigerant in the liquid reservoir 23, thereby preventing the risk of pump cavitation due to insufficient liquid refrigerant at the inlet of the refrigerant pump 4, or the risk of flow interruption due to insufficient pressure difference before and after the pump.

[0036] When the second temperature sensor 72 fails, making it impossible to calculate the supercooling degree at the inlet of the refrigerant pump 4, the pressure difference before and after the refrigerant pump 4 is directly detected to control the opening and closing of the second switch valve 62; when one or both of the first pressure sensor 81 at the inlet of the refrigerant pump 4 and the second pressure sensor 82 at the outlet of the refrigerant pump 4 fail, making it impossible to calculate the pressure difference before and after the refrigerant pump 4, the second switch valve 62 maintains a normally open state.

[0037] When it is detected for a first continuous duration (settable, 10s by default) that the pressure difference before and after the refrigerant pump 4 is greater than the sum of the pump cut-off pressure difference and the pressure difference protection value (settable 0-2bar, default 0.5bar), and when it is detected for a first continuous duration (settable, 10s by default) that the subcooling degree at the inlet of the refrigerant pump 4 is not less than the sum of the subcooling degree opening setting value and the subcooling degree protection value (settable, default 1°C), the second switch valve 62 is closed; since when the pressure difference is sufficient and the subcooling degree is sufficient, it is proved that the refrigerant pump 4 can operate normally, the second switch valve 62 can be closed.

[0038] The second control logic of this embodiment is: the first switch valve 52 remains normally closed;

[0039] After the refrigerant pump 4 is started, the head of the refrigerant pump 4 is detected: when the pressure difference before and after the pump is detected to be less than the pump cut-off pressure difference (settable, default 0.5 bar) for a first continuous duration (settable, default 10s), the first switch valve 52 is opened.

[0040] By providing a third temperature sensor 73 and a third pressure sensor 83 at one end of the second heat exchange channel 22; and by providing a fourth temperature sensor 74 and a fourth pressure sensor 84 at the other end of the second heat exchange channel 22, when the refrigerant pump 4 is started, during the operation of the unit, when the inlet and outlet water temperature difference is detected to be no greater than the temperature difference opening set value (settable, default 1°C) for a second continuous duration (settable, default 5 minutes), the first switch valve 52 is opened.

[0041] Because the temperature difference of the cold water type cold source of the heat exchanger 2 is small, the cooling capacity provided to the refrigerant in the first heat exchange channel 21 is small, which is not conducive to the full liquefaction of the gaseous refrigerant, and easily leads to insufficient liquid refrigerant at the inlet of the refrigerant pump 4. At this time, due to the opening of the first switch valve 52, a part of the liquid refrigerant at the outlet of the refrigerant pump 4 can enter one end of the heat exchanger 2 through the first bypass branch 51, so as to replenish the liquid refrigerant in the liquid reservoir 23, and prevent the risk of pump cavitation due to insufficient liquid refrigerant at the inlet of the refrigerant pump 4, or the risk of flow interruption due to insufficient pressure difference before and after the pump.

[0042] When one or both of the first pressure sensor 81 at the inlet of the refrigerant pump 4 and the second pressure sensor 82 at the outlet of the refrigerant pump 4 fail, resulting in failure to calculate the front-rear pressure difference of the refrigerant pump 4, the first switch valve 52 remains in a normally open state.

[0043] When the pressure difference before and after the pump is detected to be greater than the sum of the pump cut-off pressure difference and the pressure difference protection value (settable to 0-2 bar, default to 0.5 bar) for a first continuous duration (settable, default to 10 seconds), and when the inlet and outlet water temperature difference is detected to be greater than the sum of the temperature difference start setting value and the temperature difference protection value (settable, default to 0.5°C) for a second continuous duration (settable, default to 5 minutes) during the operation of the unit, the first switch valve 52 is closed; when the pressure difference is sufficient and the cooling capacity of the cold source is sufficient, it is proved that the refrigerant pump 4 can operate normally, and the first solenoid valve is closed at this time.

[0044] In the multi-connected refrigerant pump system for preventing cavitation described in this embodiment, the heat exchanger 2 is provided with a second heat exchange channel 22; one end of the second heat exchange channel 22 is connected to a water outlet pipe 32; the other end of the second heat exchange channel 22 is connected to a water inlet pipe 31; and a water valve 33 is provided on either the water inlet pipe 31 or the water outlet pipe 32. In the multi-connected refrigerant pump system for preventing cavitation described in this embodiment, one end of the second heat exchange channel 22 is provided with a third temperature sensor 73 and a third pressure sensor 83; the other end of the second heat exchange channel 22 is provided with a fourth temperature sensor 74 and a fourth pressure sensor 84.

[0045] Specifically, this embodiment can increase the degree of subcooling and avoid cavitation of the refrigerant pump 4 by increasing the opening of the water valve 33. If the subcooling is detected to be less than the adjustment value of the subcooling water valve 33 (settable, default 4°C) for 5 seconds, the water valve 33 enters the subcooling adjustment mode, and increases the opening of the water valve 33 by the subcooling water valve 33 step size (settable, default 5%) in each subcooling adjustment cycle (default 30 seconds). If the subcooling is detected to be greater than the adjustment value of the subcooling water valve 33 + 1°C for 5 seconds, the water valve 33 exits the subcooling adjustment mode and enters the demand adjustment mode. At this time, the opening of the water valve 33 changes linearly with the cooling demand, where the cooling demand CFC ;

[0046] Where Tc: cooling control proportional band value; Tβ: temperature control setting dead zone; T1: temperature detection value;

[0047] Ts: Temperature setting value.

[0048] In the multi-connected refrigerant pump system for preventing cavitation described in this embodiment, the outlet of each refrigerant pump 4 is connected to a one-way valve 41. The outlet of each refrigerant pump 4 is connected to the first bypass branch 51 and the main liquid pipe 13 after passing through the one-way valve 41. This arrangement ensures unidirectional movement of the refrigerant at the refrigerant pumps 4.

[0049] The embodiment of the present invention provides a multi-connected refrigerant pump system for preventing cavitation. The multi-connected refrigerant pump system for preventing cavitation includes a plurality of indoor units 12 . The plurality of indoor units 12 are connected in parallel between a main liquid pipe 13 and a main gas pipe 14 .

[0050] In the multi-connected refrigerant pump system for preventing cavitation described in this embodiment, the indoor unit 12 includes an evaporator 91, an air distribution pipe 92 disposed between one end of the evaporator 91 and the main air pipe 14, and a liquid distribution pipe 93 disposed between the other end of the evaporator 91 and the main liquid pipe 13. In the multi-connected refrigerant pump system for preventing cavitation described in this embodiment, the liquid distribution pipe 93 is equipped with an electronic expansion valve 94. In the multi-connected refrigerant pump system for preventing cavitation described in this embodiment, the air distribution pipe 92 is equipped with a fifth temperature sensor 75 and a fifth pressure sensor 85; and the liquid distribution pipe 93 is equipped with a sixth temperature sensor 76.

[0051] Specifically, in this embodiment, by providing an electronic expansion valve 94, the superheat level can be adjusted in real time according to the load level of each evaporator 91 to avoid liquid accumulation in the indoor unit 12. The specific adjustment logic is as follows:

[0052] After entering the cooling mode, adjust according to the initial superheat, maintain the initial superheat time (start timing after the initial opening time), and then adjust the superheat size according to the load situation;

[0053] The current target superheat is adjusted between the minimum superheat value and the maximum superheat value.

[0054] In addition, regarding high load and low load judgment and control:

[0055] High load judgment condition: cooling demand is greater than high load judgment demand (set value, such as 200%);

[0056] High load control mode: When the high load judgment condition is met for every continuous load judgment requirement time (default 5 minutes, adjustable), the current target superheat is reduced by 1°C.

[0057] Low load judgment condition: cooling demand is less than low load judgment demand (set value, such as 50%);

[0058] Low load control mode: When the low load judgment condition is met for every continuous load judgment requirement time (default 5 minutes, adjustable), the current target superheat will increase by 1°C.

[0059] In this embodiment, a multi-connected refrigerant pump system for preventing cavitation is described. The gas distribution pipe 92 is provided with a first control valve 95; the liquid distribution pipe 93 is provided with a second control valve 96; a third control valve 24 is provided between the other end of the first heat exchange channel 21 and the liquid reservoir 23; and a fourth control valve 15 is provided between the main liquid pipe 13 and the refrigerant pump 4. Each control valve may be a solenoid valve, which facilitates control of the refrigerant flow in each pipeline. In other embodiments, each control valve may also be a ball valve, which facilitates assembly and maintenance of components in the multi-connected system and non-stop expansion of terminal equipment.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit the scope of protection of the utility model. Although the utility model has been described in detail with reference to the preferred embodiments, ordinary technicians in this field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the utility model.

Claims

1. A multi-connected refrigerant pump system for preventing cavitation, characterized by: It includes an outdoor unit (11), an indoor unit (12), a main liquid pipe (13) and a main gas pipe (14); The outdoor unit (11) comprises a heat exchanger (2), a liquid accumulator (23), and a plurality of refrigerant pumps (4) connected in parallel; the heat exchanger (2) comprises a first heat exchange channel (21); one end of the first heat exchange channel (21) is in communication with a main gas pipe (14); the other end of the first heat exchange channel (21) is in communication with one end of the liquid accumulator (23); the other end of the liquid accumulator (23) is in communication with the inlets of all the refrigerant pumps (4); the main liquid pipe (13) is in communication with the outlets of all the refrigerant pumps (4); A first bypass branch (51) is provided between one end of the first heat exchange channel (21) and the outlets of all refrigerant pumps (4); the first bypass branch (51) is provided with a first switch valve (52); A second bypass branch (61) is provided between the other end of the first heat exchange channel (21) and the inlets of all refrigerant pumps (4); the second bypass branch (61) is provided with a second switch valve (62).

2. The multi-connected refrigerant pump system for preventing cavitation according to claim 1, characterized in that: A first temperature sensor (71) is provided at one end of the first heat exchange channel (21); a second temperature sensor (72) and a first pressure sensor (81) are provided at the inlet of the refrigerant pump (4); and a second pressure sensor (82) is provided at the outlet of the refrigerant pump (4).

3. The multi-connected refrigerant pump system for preventing cavitation according to claim 1, characterized in that: The heat exchanger (2) is provided with a second heat exchange channel (22); one end of the second heat exchange channel (22) is connected to a water outlet pipe (32); the other end of the second heat exchange channel (22) is connected to a water inlet pipe (31); The water inlet pipe (31) or the water outlet pipe (32) is provided with a water valve (33).

4. The multi-connected refrigerant pump system for preventing cavitation according to claim 3, characterized in that: A third temperature sensor (73) and a third pressure sensor (83) are provided at one end of the second heat exchange channel (22); and a fourth temperature sensor (74) and a fourth pressure sensor (84) are provided at the other end of the second heat exchange channel (22).

5. The multi-connected refrigerant pump system for preventing cavitation according to claim 1, characterized in that: The outlet of each refrigerant pump (4) is connected to a one-way valve (41); the outlet of each refrigerant pump (4) is communicated with the first bypass branch (51) and the main liquid pipe (13) through the one-way valve (41).

6. The multi-connected refrigerant pump system for preventing cavitation according to claim 1, characterized in that: The multi-connected refrigerant pump system for preventing cavitation comprises a plurality of indoor units (12); the plurality of indoor units (12) are arranged in parallel between a main liquid pipe (13) and a main gas pipe (14).

7. The multi-connected refrigerant pump system for preventing cavitation according to claim 1, characterized in that: The indoor unit (12) comprises an evaporator (91), an air distribution pipe (92) provided between one end of the evaporator (91) and the main air pipe (14), and a liquid distribution pipe (93) provided between the other end of the evaporator (91) and the main liquid pipe (13).

8. The multi-connected refrigerant pump system for preventing cavitation according to claim 7, characterized in that: The liquid distribution pipe (93) is provided with an electronic expansion valve (94).

9. The multi-connected refrigerant pump system for preventing cavitation according to claim 7, characterized in that: The gas distribution pipe (92) is provided with a fifth temperature sensor (75) and a fifth pressure sensor (85); and the liquid distribution pipe (93) is provided with a sixth temperature sensor (76).

10. The multi-connected refrigerant pump system for preventing cavitation according to claim 7, characterized in that: The gas distribution pipe (92) is provided with a first control valve (95); the liquid distribution pipe (93) is provided with a second control valve (96); a third control valve (24) is provided between the other end of the first heat exchange channel (21) and the liquid reservoir (23); and a fourth control valve (15) is provided between the main liquid pipe (13) and the refrigerant pump (4).

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