Evaporation water chilling unit with combination of centrifugal compressor and screw compressor

Abstract

The utility model discloses a centrifugal compressor and screw compressor combined evaporation water chilling unit, which belongs to the technical field of water chilling units and comprises an evaporator, a centrifugal compressor, a screw compressor, an evaporation condenser, a flash type economizer and a plate exchange type economizer. A first refrigeration cycle system is composed of a centrifugal compressor, an evaporator, an evaporative condenser and a flash type economizer, and a second refrigeration cycle system is composed of a screw compressor, an evaporator, an evaporative condenser and a plate exchange type economizer. By means of the technical scheme, the cooling capacity adjusting range of the water chilling unit is widened, in the case of large load, the first refrigeration circulation system is used, in the case of small load, the second refrigeration circulation system is used, the working conditions of the large load and the small load can meet the requirements, efficient and reliable operation can be achieved under various loads, and energy conservation and emission reduction are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of water chillers, and in particular to an evaporative water chiller combining a centrifugal compressor and a screw compressor. Background Art

[0002] With the increasing awareness of energy conservation, emission reduction, and environmental protection, and the advancement of the national western development strategy, water-scarce regions such as Xinjiang are in urgent need of high-efficiency, high-cooling-capacity, multi-operating-mode, wide-adjustment, and water-saving chillers. Among large chillers, centrifugal and screw chillers are the most widely used and the largest in number.

[0003] Centrifugal chillers have the advantages of large cooling capacity, high energy efficiency, and low noise. However, due to the inherent "surge" characteristics of centrifugal compressors, their load regulation capabilities are poor. To improve the low-load operating capacity of centrifugal chillers, most currently use a bypass valve between the condenser and evaporator. However, adjusting the load through this solution results in a large amount of energy loss, resulting in low energy efficiency of the chiller, which does not meet the goals of energy conservation and emission reduction. Screw chillers, on the other hand, do not have the "surge" characteristic at low loads and have higher energy efficiency at partial loads. However, the cooling capacity of a single head ranges from 50 to 450RT. Large cooling capacity requires multiple heads in parallel, and the unit's return oil pipeline structure and control logic are complex, resulting in high oil consumption. A large amount of lubricating oil accumulates in the evaporator, affecting heat exchange capacity and reducing the unit's energy efficiency.

[0004] In response to the above-mentioned related technologies, the applicant found that both centrifugal chillers and screw chillers have obvious shortcomings. Centrifugal chillers are not suitable for small load conditions, while screw chillers are not suitable for large load conditions. Both have limited applicability. Therefore, there is an urgent need for a chiller that can meet the requirements of both large and small load conditions to ensure efficient and reliable operation under various loads. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention provides an evaporative chiller unit comprising a centrifugal compressor and a screw compressor, which can meet the requirements of both large and small load conditions and can operate efficiently and reliably under various loads.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] An evaporative chiller combining a centrifugal compressor and a screw compressor comprises an evaporator, a centrifugal compressor, a screw compressor, an evaporative condenser, a flash economizer and a plate exchange economizer. The centrifugal compressor, the evaporator, the evaporative condenser and the flash economizer form a first refrigeration cycle system, while the screw compressor, the evaporator, the evaporative condenser and the plate exchange economizer form a second refrigeration cycle system.

[0008] Furthermore, the air outlet of the flash economizer is connected to a first air supply pipe, the first air supply pipe connects the air outlet of the flash economizer and the air supply port of the centrifugal compressor, and a first air supply regulating valve is provided on the first air supply pipe.

[0009] Furthermore, the air outlet of the plate-exchange economizer is connected to a second air supply pipe, which connects the air outlet of the plate-exchange economizer and the air supply port of the screw compressor. A second air supply regulating valve is provided on the second air supply pipe.

[0010] Furthermore, the liquid outlet of the evaporative condenser is connected to a first liquid outlet pipe, the first liquid outlet pipe connects the liquid outlet of the evaporative condenser and the liquid inlet of the flash economizer, and a first throttling expansion valve is provided on the first liquid outlet pipe.

[0011] Furthermore, the liquid outlet of the flash economizer is connected to a second liquid outlet pipe, the second liquid outlet pipe connects the liquid outlet of the flash economizer and the liquid inlet of the evaporator, and a second throttling expansion valve is provided on the second liquid outlet pipe.

[0012] Furthermore, a third liquid outlet pipe is connected to the liquid outlet of the evaporative condenser, and the third liquid outlet pipe includes a first branch and a second branch. The first branch connects the liquid outlet of the evaporative condenser and the liquid inlet of the plate exchange economizer, and the second branch connects the liquid outlet of the evaporative condenser and the liquid inlet of the plate exchange economizer. The second branch is provided with a third throttling expansion valve.

[0013] Furthermore, the liquid outlet of the plate-type economizer is connected to a fourth liquid outlet pipe, the fourth liquid outlet pipe connects the liquid outlet of the plate-type economizer and the liquid inlet of the evaporator, and a fourth throttling expansion valve is provided on the fourth liquid outlet pipe.

[0014] Furthermore, a liquid level sensor is provided on the evaporator.

[0015] In summary, compared with the prior art, the above technical solution has the following beneficial effects:

[0016] (1) Through the above technical solution, the cooling capacity adjustment range of the chiller is broadened: when the load is large, the refrigeration cycle system 1 is used, and the centrifugal compressor is operated alone to ensure efficient and stable operation, or the centrifugal compressor and the screw compressor are operated at the same time to meet the peak cooling capacity demand; when the load is small, the refrigeration cycle system 2 is used, and the screw compressor is operated alone. The centrifugal compressor makes up for the shortcoming of the small cooling capacity of the single head of the screw chiller, and the screw compressor makes up for the shortcoming of the insufficient adjustment capacity of the centrifugal chiller under small loads, so as to realize the cascade matching of the cooling capacity of the chiller, and the load adjustment range of the unit is wider, so that the working conditions of large and small loads can meet the requirements, and the unit can operate efficiently and reliably under various loads, thereby saving energy and reducing emissions;

[0017] (2) By using an evaporative condenser, the latent heat of evaporation of water is used to cool the refrigerant, which improves the heat exchange efficiency, reduces the energy consumption and water demand of the chiller system, and is more suitable for operation in areas with water shortages;

[0018] (3) Under different loads, by adjusting the opening of the first air supply regulating valve and the second air supply regulating valve, the air supply volume of the centrifugal compressor and the screw compressor is controlled to improve the load regulation capability of the unit;

[0019] (4) Under different loads, the liquid level position of the evaporator is detected by the liquid level sensor, and the opening of the first throttling expansion valve, the second throttling expansion valve and the fourth throttling expansion valve is controlled to ensure that the evaporator liquid level is always at the appropriate position, thereby improving the heat exchange capacity of the evaporator. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of an evaporative chiller that combines a centrifugal compressor and a screw compressor in an embodiment of the present invention.

[0021] Explanation of the accompanying symbols: 1. Centrifugal compressor; 1-1. First compressor exhaust pipe; 1-2. First liquid outlet pipe; 1-3. Second liquid outlet pipe; 1-4. First compressor suction pipe; 1-5. First air supply pipe; 2. Screw compressor; 2-1. Second compressor exhaust pipe; 2-2. Third liquid outlet pipe; 2-2-1. First branch; 2-2-2. Second branch; 2-3. Fourth liquid outlet pipe; 2-4. Second compressor suction pipe; 2-5. Second air supply pipe; 3. Evaporator; 4. Evaporative condenser; 5. Flash economizer; 6. Plate exchange economizer; 7. First throttling expansion valve; 8. Second throttling expansion valve; 9. Third throttling expansion valve; 10. Fourth throttling expansion valve. DETAILED DESCRIPTION

[0022] The principles and features of the present invention are described below in conjunction with all the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0023] The embodiment of the present invention discloses an evaporative water chiller unit combining a centrifugal compressor and a screw compressor.

[0024] Reference Figure 1 An evaporative chiller combining a centrifugal compressor and a screw compressor includes an evaporator 3, a centrifugal compressor 1, a screw compressor 2, an evaporative condenser 4, a flash economizer 5 and a plate exchange economizer 6. The centrifugal compressor 1, the evaporator 3, the evaporative condenser 4 and the flash economizer 5 form a refrigeration cycle system 1, and the screw compressor 2, the evaporator 3, the evaporative condenser 4 and the plate exchange economizer 6 form a refrigeration cycle system 2.

[0025] The exhaust port of centrifugal compressor 1 is connected to the air inlet of evaporative condenser 4 via first compressor exhaust pipe 1-1. The liquid outlet of evaporative condenser 4 is connected to flash economizer 5 via first liquid outlet pipe 1-2, on which first throttling expansion valve 7 is installed. The air outlet of flash economizer 5 is connected to the air supply port of centrifugal compressor 1 via first air supply pipe 1-5. The liquid outlet of flash economizer 5 is connected to the liquid inlet of evaporator 3 via second liquid outlet pipe 1-3, on which second throttling expansion valve 8 is installed. The air outlet of evaporator 3 is connected to the air intake of centrifugal compressor 11 via first compressor intake pipe 1-4, forming a closed refrigeration cycle system.

[0026] The exhaust port of screw compressor 2 is connected to the air inlet of evaporative condenser 4 through second compressor exhaust pipe 2-1. The liquid outlet of evaporative condenser 4 is connected to third liquid outlet pipe 2-2, which branches into a first branch 2-2-1 and a second branch 2-2-2. First branch 2-2-1 is the main branch, directly connected to the liquid inlet of plate-type economizer 6. Second branch 2-2-2 is the auxiliary branch. A third throttling expansion valve 9 is installed on second branch 2-2-2. After throttling, the refrigerant is connected to the liquid inlet of plate-type economizer 6. The air outlet of the plate exchange economizer 6 is connected to the air supply port of the screw compressor 2 through the second air supply pipe 2-5, the liquid outlet of the plate exchange economizer 6 is connected to the liquid inlet of the evaporator 3 through the fourth liquid outlet pipe 2-3, and a fourth throttling expansion valve 10 is provided on the fourth liquid outlet pipe 2-3. The air outlet of the evaporator 3 is connected to the air intake port of the screw compressor 2 through the second compressor intake pipe 2-4, forming a closed refrigeration cycle system II.

[0027] Refrigeration cycle system 1 and refrigeration cycle system 2 are independent and do not interfere with each other. Centrifugal compressor 1 and screw compressor 2 can operate independently or simultaneously. This makes the chiller's cooling capacity adjustment more flexible, covers a wider operating range, and is more energy-efficient. Multiple centrifugal compressors 1 and 2 can be installed to match the customer's cooling capacity needs and adjustment range, thus expanding the chiller's cooling capacity adjustment range.

[0028] When the load is large, the refrigeration cycle system 1 is used, and the centrifugal compressor 1 is operated alone to ensure efficient and stable operation, or the centrifugal compressor 1 and the screw compressor 2 are operated at the same time to meet the peak cooling capacity demand; when the load is small, the refrigeration cycle system 2 is used, and the screw compressor 2 is operated alone. The centrifugal compressor 1 makes up for the shortcoming of the small cooling capacity of the single head of the screw chiller, and the screw compressor 2 makes up for the shortcoming of the insufficient adjustment ability of the centrifugal chiller under small loads, so as to realize the cascade matching of the cooling capacity of the chiller and the wider load adjustment range of the unit, so that the requirements can be met under both large and small load conditions, and the unit can operate efficiently and reliably under various loads, thereby saving energy and reducing emissions.

[0029] In the evaporator 3, the refrigerant evaporates and absorbs heat, and the secondary coolant exchanges heat with the refrigerant through the heat exchange tube, so that the temperature of the secondary coolant entering the evaporator 3 is reduced, providing cooling capacity for the client.

[0030] Inside the evaporative condenser 4, high-temperature and high-pressure refrigerant gas passes through the condensation drain pipe in the evaporative condenser 4, causing the high-temperature gaseous refrigerant to exchange heat with the spray water and air outside the drain pipe. That is, after the gaseous refrigerant enters the drain pipe from the top, it is gradually condensed into liquid refrigerant from top to bottom, and the wind force of the fan is used to make the spray water completely and evenly cover the surface of the coil. The water is greatly improved by the wind, which greatly improves the heat exchange effect. The spray water with increased temperature is partially converted into gaseous state, and a large amount of heat is carried away by the wind using the latent heat of vaporization of the water. The water droplets in the hot air are intercepted by the high-efficiency dehydrator and scattered into the heat exchange layer of the water spray plate with the rest of the water that has absorbed heat. It is cooled by the air flowing through, the temperature is reduced, and it enters the water tank and continues to circulate through the circulating water pump, reducing the water circulation volume and saving water resources. By matching with the evaporative condenser 4, the latent heat of vaporization of water is used to cool the refrigerant, which improves the heat exchange efficiency, reduces the energy consumption and water demand of the chiller system, and is more suitable for operation in areas with water shortages.

[0031] The liquid outlet of the evaporative condenser 4 is connected to a first liquid outlet pipe 1-2, which connects the liquid outlet of the evaporative condenser 4 with the liquid inlet of the flash economizer 5. A first throttling expansion valve 7 is provided on the first liquid outlet pipe 1-2. The liquid outlet of the flash economizer 5 is connected to a second liquid outlet pipe 1-3, which connects the liquid outlet of the flash economizer 5 with the liquid inlet of the evaporator 3. A second throttling expansion valve 8 is provided on the second liquid outlet pipe 1-3.

[0032] The exhaust port of centrifugal compressor 1 is connected to the air inlet of evaporative condenser 4 via first compressor exhaust pipe 1-1. The liquid outlet of evaporative condenser 4 is connected to first liquid outlet pipe 1-2, which is equipped with a first throttling expansion valve 7. First liquid outlet pipe 1-2 is connected to the liquid inlet of flash economizer 5. The air outlet of flash economizer 5 is connected to the air supply port of centrifugal compressor 1 via first air supply pipe 1-5. The liquid outlet of flash economizer 5 is connected to second liquid outlet pipe 1-3, which is equipped with a second throttling expansion valve 8. Second liquid outlet pipe 1-3 is connected to the liquid inlet of evaporator 3. The air outlet of evaporator 3 is connected to the air intake of centrifugal compressor 1 via first compressor intake pipe 1-4.

[0033] The liquid outlet of the evaporative condenser 4 is connected to a third liquid outlet pipe 2-2, and the third liquid outlet pipe 2-2 includes a first branch 2-2-1 and a second branch 2-2-2. The first branch 2-2-1 connects the liquid outlet of the evaporative condenser 4 and the liquid inlet of the plate exchange economizer 6, and the second branch 2-2-2 connects the liquid outlet of the evaporative condenser 4 and the liquid inlet of the plate exchange economizer 6. The second branch 2-2-2 is provided with a third throttling expansion valve 9.

[0034] The liquid outlet of the plate-type economizer 6 is connected to a fourth liquid outlet pipe 2 - 3 , which connects the liquid outlet of the plate-type economizer 6 and the liquid inlet of the evaporator 3 . A fourth throttling expansion valve 10 is provided on the fourth liquid outlet pipe 2 - 3 .

[0035] The exhaust port of the screw compressor 2 is connected to the air inlet of the evaporative condenser 4 through the second compressor exhaust pipe 2-1. The liquid outlet of the evaporative condenser 4 is connected to the third liquid outlet pipe 2-2. The third liquid outlet pipe 2-2 is divided into a first branch 2-2-1 and a second branch 2-2-2. The first branch 2-2-1 is connected to the liquid inlet of the plate exchange economizer 6. The second branch 2-2-2 is provided with a third throttling expansion valve 9. The second branch 2-2-2 is connected to the liquid inlet of the plate exchange economizer 6. The air outlet of the plate exchange economizer 6 is connected to the air supply port of the screw compressor 2 through the second air supply pipe 2-5. The liquid outlet of the plate exchange economizer 6 is connected to the fourth liquid outlet pipe 2-3. The fourth liquid outlet pipe 2-3 is provided with a fourth throttling expansion valve 10. The fourth liquid outlet pipe 2-3 is connected to the liquid inlet of the evaporator 3. The air outlet of the evaporator 3 is connected to the air intake of the screw compressor 2 through the second compressor intake pipe 2-4.

[0036] The outlet of the flash economizer 5 is connected to a first air supply pipe 1-5, which connects the outlet of the flash economizer 5 to the air supply port of the centrifugal compressor 1. A first air supply regulating valve is installed on the first air supply pipe 1-5. The outlet of the plate-type economizer 6 is connected to a second air supply pipe 2-5, which connects the outlet of the plate-type economizer 6 to the air supply port of the screw compressor 2. A second air supply regulating valve is installed on the second air supply pipe 2-5. Under different loads, the openings of the first and second air supply regulating valves are adjusted to control the air supply volume of the centrifugal compressor 1 and screw compressor 2, thereby improving the load regulation capability of the unit.

[0037] A liquid level sensor is installed on the evaporator 3. Under different load conditions, the liquid level sensor detects the liquid level in the evaporator 3 and controls the openings of the first throttling expansion valve 7, the second throttling expansion valve 8, and the fourth throttling expansion valve 10 to ensure that the liquid level in the evaporator 3 is always at the appropriate level, thereby improving the heat exchange capacity of the evaporator 3.

[0038] In the flash economizer 5, the refrigerant, throttled by the first throttling expansion valve 7, flashes, separating the gas and liquid. The gas refrigerant then flows through the first air supply pipe 1-5 to supply air to the centrifugal compressor 1. This method of supplying air and increasing heat enthalpy through the throttling system before the flash economizer 5 is more suitable for large centrifugal units. By installing the flash economizer 5 to supply air and increase heat enthalpy to the centrifugal compressor 1, energy savings of 3% to 5% can be achieved.

[0039] Within the plate-type economizer 6, the refrigerant passing through the first branch 2-2-1 and the refrigerant throttled by the third throttling expansion valve 9 in the second branch 2-2-2 exchange heat within the plate-type economizer. The refrigerant in the first branch 2-2-1 releases heat within the plate-type economizer, increasing the degree of subcooling, and flows out through the fourth liquid outlet pipe 2-3. The refrigerant in the second branch 2-2-2 absorbs heat and evaporates within the plate-type economizer, replenishing air to the screw compressor 2 through the second air supply pipe 2-5. This method of increasing heat enthalpy through air supply in the subcooler system is more suitable for small screw units. By installing the plate-type economizer 6 to increase heat enthalpy in the screw compressor 2, energy savings of 3% to 5% can be achieved.

[0040] The evaporative chiller system, which incorporates a centrifugal and screw compressors, operates on the principle that refrigeration cycle system 1 and refrigeration cycle system 2 are independent and non-interfering. Centrifugal compressor 1 and screw compressor 2 can operate independently or simultaneously, making the chiller more flexible in cooling capacity adjustment, extending the operating range, and achieving greater energy efficiency.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An evaporative chiller unit combining a centrifugal compressor and a screw compressor, characterized in that: The invention comprises an evaporator (3), a centrifugal compressor (1), a screw compressor (2), an evaporative condenser (4), a flash economizer (5) and a plate exchange economizer (6). The centrifugal compressor (1), the evaporator (3), the evaporative condenser (4) and the flash economizer (5) form a first refrigeration cycle system, and the screw compressor (2), the evaporator (3), the evaporative condenser (4) and the plate exchange economizer (6) form a second refrigeration cycle system.

2. The evaporative chiller unit comprising a centrifugal compressor and a screw compressor according to claim 1, characterized in that: The air outlet of the flash economizer (5) is connected to a first air supply pipe (1-5), the first air supply pipe (1-5) connects the air outlet of the flash economizer (5) and the air supply port of the centrifugal compressor (1), and a first air supply regulating valve is provided on the first air supply pipe (1-5).

3. The evaporative chiller unit comprising a centrifugal compressor and a screw compressor according to claim 1, characterized in that: The air outlet of the plate-exchange economizer (6) is connected to a second air supply pipe (2-5), the second air supply pipe (2-5) connects the air outlet of the plate-exchange economizer (6) and the air supply port of the screw compressor (2), and a second air supply regulating valve is provided on the second air supply pipe (2-5).

4. The evaporative chiller unit comprising a centrifugal compressor and a screw compressor according to claim 1, characterized in that: The liquid outlet of the evaporative condenser (4) is connected to a first liquid outlet pipe (1-2), the first liquid outlet pipe (1-2) connects the liquid outlet of the evaporative condenser (4) and the liquid inlet of the flash economizer (5), and a first throttling expansion valve (7) is provided on the first liquid outlet pipe (1-2).

5. The evaporative chiller unit comprising a centrifugal compressor and a screw compressor according to claim 1, characterized in that: The liquid outlet of the flash economizer (5) is connected to a second liquid outlet pipe (1-3), the second liquid outlet pipe (1-3) connects the liquid outlet of the flash economizer (5) and the liquid inlet of the evaporator (3), and a second throttling expansion valve (8) is provided on the second liquid outlet pipe (1-3).

6. The evaporative chiller unit comprising a centrifugal compressor and a screw compressor according to claim 1, characterized in that: The liquid outlet of the evaporative condenser (4) is connected to a third liquid outlet pipe (2-2), the third liquid outlet pipe (2-2) comprises a first branch (2-2-1) and a second branch (2-2-2), the first branch (2-2-1) connects the liquid outlet of the evaporative condenser (4) and the liquid inlet of the plate exchange economizer (6), the second branch (2-2-2) connects the liquid outlet of the evaporative condenser (4) and the liquid inlet of the plate exchange economizer (6), and the second branch (2-2-2) is provided with a third throttling expansion valve (9).

7. The evaporative chiller unit comprising a centrifugal compressor and a screw compressor according to claim 1, characterized in that: The liquid outlet of the plate-exchange economizer (6) is connected to a fourth liquid outlet pipe (2-3), the fourth liquid outlet pipe (2-3) connects the liquid outlet of the plate-exchange economizer (6) and the liquid inlet of the evaporator (3), and a fourth throttling expansion valve (10) is provided on the fourth liquid outlet pipe (2-3).

8. The evaporative chiller unit comprising a centrifugal compressor and a screw compressor according to claim 1, characterized in that: The evaporator (3) is provided with a liquid level sensor.

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