Air-cooled refrigeration and freezing dual-machine parallel evaporation cold screw unit

Abstract

The application discloses a kind of air-cooled freezing refrigeration double-machine parallel evaporation cold screw unit, it is related to refrigeration machine technical field, including frame and evaporator, compressor is installed on frame;It is further including oil separator being arranged on frame, it is used to receive oil-gas mixture from the exhaust port of compressor and separate lubricating oil;Condenser for condensing refrigerant vapor from oil separator;Liquid refrigerant storage tank for storing liquid refrigerant flowing from condenser;Economizer with inlet and outlet.The air-cooled freezing refrigeration double-machine parallel evaporation cold screw unit utilizes the cold refrigerant of system itself as cold source, efficiently cools lubricating oil by oil cooler, significantly reduces oil return temperature, improves the lubrication and working conditions of compressor, improves efficiency and reliability.Economizer improves the supercooling degree of main cycle, oil cooler improves oil cooling efficiency, and all components are integrated in a frame, compact structure, small footprint.

Description

Technical Field

[0001] This invention relates to the field of refrigeration technology, and more specifically to a parallel evaporative screw chiller unit with air-cooled refrigeration and freezing systems. Background Technology

[0002] In the industrial refrigeration and cold storage sector, air-cooled heat pump screw chillers are widely used due to their large capacity and high reliability. However, most existing refrigeration units for cold storage adopt a split or modular design, meaning that core components such as compressors, oil separators, condensers, and liquid receivers are relatively independent. This requires complex piping connections and system assembly at the application site, resulting in disadvantages such as non-compact structure, large footprint, and inconvenient installation and maintenance. Furthermore, the control systems of traditional units are relatively simple, lacking precise monitoring and visualization of key operating parameters (such as oil temperature), failing to provide early warning and intelligent protection, and posing safety hazards.

[0003] A low-temperature air-cooled heat pump system with direct-drive two-stage and dual-machine parallel switching capability, disclosed in publication number CN107702369A, includes two parallel-connected first and second screw compressors. An oil separator is connected to both the first and second screw compressors. An exhaust pipe is provided between the exhaust port of the first and second screw compressors, and an exhaust shut-off valve is installed on the exhaust pipe. A first four-way reversing valve and a second four-way reversing valve are located at the outlet of the oil separator. An evaporator is connected to the outlets of both the first and second four-way reversing valves. By combining compressor design and two-stage compression design, the operating efficiency of the air-cooled heat pump unit, especially its low-temperature operating efficiency, is significantly improved, as is its heating capacity.

[0004] During operation, the high-temperature, high-pressure refrigerant vapor discharged from the compressor contains lubricating oil. Although separated by an oil separator, the temperature of the separated lubricating oil remains high. If this high-temperature lubricating oil returns directly to the compressor, it will severely affect the compressor's cooling and lubrication, leading to decreased compressor efficiency, increased wear, and a shortened unit lifespan. Summary of the Invention

[0005] The purpose of this invention is to provide a parallel air-cooled refrigeration and freezing dual-unit evaporative screw chiller unit to solve the above-mentioned problems.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a dual-unit parallel evaporative screw chiller with air cooling and refrigeration, comprising a frame and an evaporator, wherein a compressor is mounted on the frame;

[0007] It also includes an oil separator mounted on the frame, which is used to receive the oil-gas mixture from the compressor exhaust port and separate the lubricating oil;

[0008] A condenser for condensing refrigerant vapor from the oil separator;

[0009] A receiver for storing the liquid refrigerant flowing out of the condenser;

[0010] An economizer with import and export functions, whose import and export functions are connected to a liquid storage tank and an evaporator, respectively;

[0011] It also includes a lubricating oil cooling circuit, which contains an oil cooler for cooling the lubricating oil;

[0012] The first channel of the oil cooler is connected in series between the oil drain port of the oil separator and the lubricating oil inlet of the compressor, and the second channel of the oil cooler is connected to the economizer.

[0013] Preferably, the frame is divided into a first region and a second region, with the condenser and oil cooler centrally located in the second region, and heat dissipation louvers provided on the side of the second region.

[0014] Preferably, the device also includes a gas-liquid separator, and a connecting pipe is provided between the gas-liquid separator and the evaporator, wherein the outlet of the gas-liquid separator is connected to the inlet of the compressor.

[0015] Preferably, the connecting pipe is provided with a pressure-reducing structure to reduce airflow disturbance.

[0016] Preferably, the pressure-reducing structure is a pipe section whose flow cross-section gradually expands in a stepped manner along the air intake direction.

[0017] Preferably, the stepped diffuser section includes at least two stages of diffusers connected sequentially along the intake direction with progressively increasing inner diameters.

[0018] Preferably, an internal flow perforated plate is provided at the connection between two adjacent expansion tubes.

[0019] Preferably, the lubricating oil cooling circuit further includes an oil filter disposed between the oil cooler and the compressor.

[0020] Preferably, a liquid supply filter tank is also included, which is disposed between the outlet of the liquid reservoir and the inlet of the economizer.

[0021] Preferably, the system also includes a control system, which includes a sensing unit for detecting unit operating parameters.

[0022] The control unit that is connected to the sensing unit via signals;

[0023] The PLC display screen, connected to the control unit, is used to visualize the operating parameters.

[0024] In the above technical solution, the air-cooled refrigeration and cooling dual-unit parallel evaporative screw chiller provided by the present invention has the following beneficial effects: Utilizing the system's own refrigerant as a cold source, and efficiently cooling the lubricating oil through an oil cooler, significantly reducing the return oil temperature, improving the compressor's lubrication and operating conditions, and increasing efficiency and reliability. The economizer improves the subcooling of the main cycle, the oil cooler improves oil cooling efficiency, and all components are integrated into a single frame, resulting in a compact structure and small footprint. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0026] Figure 1 This is a schematic diagram of the overall three-dimensional structure provided in an embodiment of the present invention;

[0027] Figure 2 This is a three-dimensional structural schematic diagram of another aspect provided in an embodiment of the present invention;

[0028] Figure 3 A front view provided for an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the internal structure provided in an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of the pressure reduction structure provided in an embodiment of the present invention;

[0031] Figure 6 This is a schematic diagram of the internal structure of the pressure-reducing structure provided in an embodiment of the present invention;

[0032] Figure 7 This is a flowchart provided for an embodiment of the present invention.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1. Frame; 2. Electrical control box; 4. Gas-liquid separator; 5. Liquid receiver; 6. Compressor; 7. Oil separator; 8. Connecting pipe; 9. Oil filter; 10. Liquid supply filter tank; 11. Pressure reducing structure; 111. First expansion pipe; 112. Second expansion pipe; 113. Third expansion pipe; 114. First perforated plate; 115. Second perforated plate; 12. Economizer; 13. Condenser; 14. Evaporator; 15. Oil cooler. Detailed Implementation

[0035] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0036] like Figures 1-7 As shown, a dual-unit parallel evaporative screw chiller unit with air cooling and refrigeration includes a frame 1 and an evaporator 14, with a compressor 6 installed on the frame 1;

[0037] It also includes an oil separator 7 mounted on the frame 1, which is used to receive the oil-gas mixture from the exhaust port of the compressor 6 and separate the lubricating oil;

[0038] Condenser 13 is used to condense refrigerant vapor from oil separator 7;

[0039] Receiver 5 is used to store the liquid refrigerant flowing out of condenser 13;

[0040] An economizer 12 has an import and export device, whose import and export are connected to a liquid storage tank 5 and an evaporator 14, respectively.

[0041] It also includes a lubricating oil cooling circuit, which includes an oil cooler 15 for cooling the lubricating oil;

[0042] The first channel of the oil cooler 15 is connected in series between the oil drain port of the oil separator 7 and the lubricating oil inlet of the compressor 6, and the second channel of the oil cooler 15 is connected to the economizer 12.

[0043] Specifically, the frame 1 is internally divided into a first area and a second area. The first area also houses the electrical control box 2, while the condenser 13 and oil cooler 15 are located in the second area. The second area is equipped with three-sided heat dissipation louvers to facilitate customer maintenance and repair while ensuring unit heat dissipation. Multiple screw compressors 6 can be operated in parallel, with the discharge port of each compressor 6 connected to a shared oil separator 7 via piping. The oil separator 7 efficiently separates the lubricating oil from the high-temperature, high-pressure oil-gas mixture discharged from the compressor 6, preventing excessive lubricating oil from entering the subsequent condensation circuit and affecting heat exchange efficiency.

[0044] The gas outlet of the oil separator 7 is connected to the inlet of the condenser 13 via a pipeline. The condenser 13 is preferably an evaporative condenser, which utilizes the principle of heat absorption during water evaporation to efficiently condense high-temperature refrigerant vapor into liquid refrigerant. The liquid outlet of the condenser 13 is connected to the inlet of the liquid receiver 5.

[0045] The outlet of the receiver 5 is connected to the economizer 12 via a pipeline. The main inlet of the economizer 12 is connected to the liquid supply filter tank 10, and the main outlet supplies subcooled liquid refrigerant to the evaporator 14 in the cold storage via the main liquid supply pipeline. In the economizer 12, part of the liquid refrigerant evaporates at a throttling rate, absorbing heat from the other part of the mainstream liquid refrigerant, thus achieving a greater degree of subcooling and significantly improving system efficiency.

[0046] Furthermore, the high-temperature lubricating oil separated from the oil separator 7 is led through a pipeline to the first channel of the oil cooler 15 (i.e., Figure 7 The lubricating oil flows through the inlet of the oil cooler 15 (shown in the diagram). The lubricating oil is cooled as it flows through the first channel of the oil cooler 15 and then flows out from the outlet of the first channel. Finally, the clean and cooled lubricating oil is returned to the lubricating oil inlet of each compressor 6, completing the lubricating oil circulation. The placement of the oil filter 9 is crucial; it ensures the quality of the lubricating oil returning to the compressor 6 and extends the service life of the compressor 6.

[0047] In the above technology, the system's own refrigerant is used as a cold source, and the lubricating oil is efficiently cooled by the oil cooler 15, which significantly reduces the return oil temperature, improves the lubrication and operating conditions of the compressor 6, and increases efficiency and reliability. The economizer 12 increases the subcooling of the main cycle, the oil cooler 15 improves the oil cooling efficiency, and all components are integrated into a single frame, resulting in a compact structure and small footprint.

[0048] As a further embodiment of the present invention, it also includes a gas-liquid separator 4, and a connecting pipe 8 is provided between the gas-liquid separator 4 and the evaporator 14, and the gas outlet of the gas-liquid separator 4 is connected to the gas inlet of the compressor 6.

[0049] Specifically, in cold storage or spaces requiring refrigeration, liquid refrigerant flows within the pipes of evaporator 14, absorbing heat from the air or refrigerant (such as brine) flowing outside the evaporator and boiling violently, thus fulfilling its refrigeration function. However, the refrigerant does not completely evaporate into vapor, but rather forms a low-temperature, low-pressure gas-liquid mixture. If this gas-liquid mixture directly enters the compressor, the liquid droplets within it will cause liquid slugging impact on the compressor valve plates or screw rotor, severely damaging the equipment. Therefore, a gas-liquid separator 4 is used to improve the above problems. Preferably, the gas-liquid separator 4 has a vertical tank structure, such as the S-QF-50 type gas-liquid separator. The gas-liquid separator 4 has an air inlet at the top, connected to the air return port of the evaporator 14 inside the cold storage via a connecting pipe 8. The interior of the gas-liquid separator 4 can be equipped with filters or baffles, utilizing gravity and inertia to achieve efficient gas-liquid separation. After separation, the liquid refrigerant accumulates at the bottom of the tank and slowly returns to the system through the lower oil return hole under its own gravity or pressure difference. The less dense refrigerant vapors accumulate at the top and are eventually drawn into the compressor 6.

[0050] As a further embodiment of the present invention, the connecting pipe 8 is provided with a pressure reducing structure 11 for reducing airflow disturbance.

[0051] Specifically, the pressure-reducing structure 11 is a pipe section whose flow cross-section gradually expands in a stepped manner along the air intake direction (e.g., Figure 5 and Figure 6 As shown), the stepped diffuser section includes at least two stages of diffusers connected sequentially along the intake direction, with the inner diameter increasing at each stage. The pressure-reducing structure 11 includes a first diffuser 111, a second diffuser 112, and a third diffuser 113 (structure as shown). Figure 6 As shown in the figure, a first perforated plate 114 is fixedly installed at the connection between the first expansion tube 111 and the second expansion tube 112, while a second perforated plate 115 in the shape of a frustum is fixedly installed at the connection between the second expansion tube 112 and the third expansion tube 113. When the pulsating airflow enters, the airflow passes through the first expansion tube 111, the second expansion tube 112 and the third expansion tube 113 with progressively increasing inner diameters. According to the principles of fluid mechanics, under the condition that the volumetric flow rate remains basically unchanged, the expansion of the flow cross section will inevitably lead to a significant reduction in the airflow velocity. Therefore, part of the dynamic pressure (kinetic energy) of the airflow is converted into static pressure (potential energy) in this process. This not only plays a preliminary pressure stabilization role, making the outlet pressure more stable, but also creates more favorable conditions for subsequent gas-liquid separation.

[0052] Furthermore, as the airflow passes through the perforated plates at each stage, larger vortices are broken into smaller ones, effectively consuming airflow energy. This breaking-up process, along with the intense friction between the fluid and the orifice walls, consumes a significant amount of airflow energy, converting it into heat and dissipating it. Moreover, the structures of the first perforated plate 114 and the second perforated plate 115 can also partially cancel out the propagation of existing noise by generating sound waves with opposite phases, thereby reducing noise at its source and significantly mitigating pressure fluctuations. This design ensures a more stable airflow entering the gas-liquid separator 4, improves separation efficiency, and reduces the overall operating noise of the system.

[0053] As a further embodiment of the present invention, the lubricating oil cooling circuit also includes an oil filter 9 disposed between the oil cooler 15 and the compressor 6.

[0054] Specifically, in the lubricating oil cooling circuit, the lubricating oil flowing out from the first channel of the oil cooler 15, although already cooled, may precipitate tiny colloidal particles or contain extremely small debris caused by metal wear after experiencing high temperature and the cooling process. If these impurities return directly to the compressor 6, they will exacerbate the wear of precision moving parts such as bearings and rotors.

[0055] Therefore, in this embodiment, an oil filter 9 is installed in series immediately after the oil cooler 15 on the lubricating oil return line. The lubricating oil flows through the oil filter 9 before entering the compressor 6, which traps impurities in the lubricating oil, thereby ensuring that the lubricating oil returning to the compressor 6 is always highly clean, extending the maintenance cycle and service life of the compressor 6.

[0056] As a further embodiment of the present invention, a liquid supply filter tank 10 is also provided between the outlet of the liquid reservoir 5 and the inlet of the economizer 12.

[0057] Specifically, the liquid supply filter tank 10 is equipped with a pressure detection device. When the pressure difference across the filter is too large, a signal is issued to prompt replacement. When the detected pressure difference exceeds a preset safety threshold (this threshold is set according to the system's rated flow rate and the filter element's capacity), the control unit will immediately issue an audible and visual alarm signal through the human-machine interface (such as a PLC display screen) and prompt "Liquid supply filter tank clogged, please replace it in time." This design eliminates the need for operators to guess based on experience or periodically stop the machine for replacement. The setup of this device is common knowledge to those skilled in the art and will not be elaborated here. All liquid refrigerant flowing from the liquid receiver 5 to the economizer 12 must pass through this filter, and impurities are effectively filtered out, ensuring the efficient and reliable operation of the economizer 12 and the evaporator 14.

[0058] As a further embodiment of the present invention, it also includes a control system, which includes a sensing unit for detecting unit operating parameters;

[0059] The control unit that is connected to the sensing unit via signals;

[0060] The PLC display screen, connected to the control unit, is used to visualize the operating parameters.

[0061] Specifically, a pressure sensor (range, for example, 0-3.0 MPa) is installed on the discharge manifold of compressor 6 to monitor the critical discharge pressure; a low-pressure sensor (range, for example, -0.1-1.5 MPa) is installed on the common suction manifold of compressor 6 to monitor the suction pressure. These pressure signals directly reflect the system's condensing and evaporating pressure conditions.

[0062] Furthermore, a first temperature sensor can be installed near the exhaust port of compressor 6 to monitor the exhaust temperature and prevent compressor 6 from overheating. A second temperature sensor can be installed on the lubricating oil outlet pipe of oil cooler 15 or at the lubricating oil point of compressor 6 to accurately monitor the lubricating oil temperature returning to the compressor, which is a key indicator for evaluating lubrication and cooling performance. In addition, a third temperature sensor can be optionally installed to monitor ambient temperature or condenser inlet air temperature, providing data support for the adaptive operation of the system.

[0063] The aforementioned signals are transmitted to the control unit. The control unit has a pre-set program that continuously compares the collected parameters with preset safety thresholds and accurately detects various parameters such as exhaust pressure, intake pressure, and refrigeration oil temperature through charts or bar graphs, making the parameters visual. For reference, a compressor pressure detection device disclosed in CN119914516A is mentioned, which is prior art and will not be described in detail here.

[0064] Working Principle: The gas-liquid mixture of refrigerant in evaporator 14 enters gas-liquid separator 4 through connecting pipe 8 for gas-liquid separation. The separated dry vapor is drawn into compressor 6 and compressed into high-temperature, high-pressure gas. This gas mixes with lubricating oil and enters oil separator 7, where most of the lubricating oil is separated. The separated high-temperature refrigerant vapor enters evaporative condenser 13 and is condensed into high-pressure liquid. The liquid refrigerant is stored in liquid receiver 5, and then filtered through liquid supply filter 10 before entering economizer 12. In economizer 12, a portion of the liquid is throttled to evaporate and cool the main liquid flow, giving it subcooling and thus significantly improving system energy efficiency.

[0065] The subcooled liquid refrigerant is transported to the evaporator 14, and the low-temperature, low-pressure gas-liquid mixture formed after evaporation returns to the gas-liquid separator 4, thus completing the entire main refrigeration cycle.

[0066] Meanwhile, the high-temperature lubricating oil separated from the oil separator 7 is led to the first channel of the oil cooler 15 (e.g., Figure 7 The lubricating oil flow channel shown in the diagram) diverts a small stream of low-temperature refrigerant from the outlet of the economizer 12, which serves as a cooling source as it enters the second channel of the oil cooler 15 (as shown in the diagram). Figure 7 As shown in the refrigerant flow channel, within the oil cooler 15, the low-temperature refrigerant and the high-temperature lubricating oil undergo efficient heat exchange, achieving sufficient cooling of the lubricating oil.

[0067] After cooling, the lubricating oil flows through the oil filter 9 to remove impurities. The clean, low-temperature lubricating oil then returns to the lubrication points of the compressor 6, ensuring reliable operation and a long service life of the compressor. The refrigerant used for cooling absorbs heat and evaporates before returning to the low-pressure side to participate in the main circulation.

[0068] In the aforementioned process, the unit is equipped with a control system centered around a PLC display screen. Key parameters such as exhaust pressure, intake pressure, and oil temperature are monitored in real time using pressure and temperature sensors installed at critical nodes. These parameters are centrally displayed on the PLC screen. The control unit compares the real-time data with preset safety thresholds. When an anomaly occurs (such as excessive pressure or excessive oil temperature), the system automatically implements protective measures such as alarms, frequency reduction, or shutdown to ensure the unit always operates safely and efficiently.

[0069] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A dual-unit parallel evaporative screw chiller unit for air-cooled refrigeration and freezing, comprising a frame (1) and an evaporator (14), characterized in that, A compressor (6) is mounted on the frame (1); It also includes an oil separator (7) disposed on the frame (1), which is used to receive the oil-gas mixture from the exhaust port of the compressor (6) and separate the lubricating oil; A condenser (13) for condensing refrigerant vapor from the oil separator (7); A liquid receiver (5) for storing the liquid refrigerant flowing out from the condenser (13); An economizer (12) with an import and an export is connected to a liquid storage tank (5) and an evaporator (14) respectively. It also includes a lubricating oil cooling circuit, which includes an oil cooler (15) for cooling the lubricating oil. The first channel of the oil cooler (15) is connected in series between the oil outlet of the oil separator (7) and the lubricating oil inlet of the compressor (6), and the second channel of the oil cooler (15) is connected to the economizer (12). It also includes a gas-liquid separator (4), and a connecting pipe (8) is provided between the gas-liquid separator (4) and the evaporator (14), wherein the outlet of the gas-liquid separator (4) is connected to the inlet of the compressor (6); The connecting pipe (8) is provided with a pressure reducing structure (11) for reducing airflow disturbance. The pressure-reducing structure (11) is a stepped expanding pipe section with a flow cross section that gradually expands in a stepped manner along the air intake direction. The stepped diffuser section includes at least two stages of diffusers connected sequentially along the intake direction, with the inner diameter increasing step by step. An internal flow perforated plate is provided at the connection between two adjacent expansion tubes.

2. The air-cooled refrigeration and freezing dual-unit parallel evaporative screw chiller unit according to claim 1, characterized in that, The frame (1) is divided into a first region and a second region. The condenser (13) and the oil cooler (15) are concentrated in the second region, and the second region is provided with heat dissipation louvers on the side.

3. The air-cooled refrigeration and freezing dual-unit parallel evaporative screw chiller unit according to claim 1, characterized in that, The lubricating oil cooling circuit also includes an oil filter (9) disposed between the oil cooler (15) and the compressor (6).

4. The air-cooled refrigeration and freezing dual-unit parallel evaporative screw chiller unit according to claim 1, characterized in that, It also includes a liquid supply filter tank (10) located between the outlet of the liquid reservoir (5) and the inlet of the economizer (12).

5. The air-cooled refrigeration and freezing dual-unit parallel evaporative screw chiller unit according to claim 1, characterized in that, It also includes a control system, which includes a sensing unit for detecting unit operating parameters; The control unit that is connected to the sensing unit via signals; The PLC display screen, connected to the control unit, is used to visualize the operating parameters.

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