Industrial centrifugal water chilling unit capable of realizing minimum pressure protection of evaporator

Abstract

The utility model discloses an industrial centrifugal water chilling unit capable of achieving minimum pressure protection of an evaporator. The industrial centrifugal water chilling unit mainly comprises the evaporator, a condenser, a compressor and a PLC. The technical problem that due to the fact that the pressure of an evaporator of an existing centrifugal water chilling unit is too low, the suction pressure of a compressor cannot be guaranteed, frequent starting and stopping are needed, and equipment accidents or production accidents are caused is solved. According to the utility model, through the PLC control system, the throttle pipe and the blowdown pipe are arranged between the evaporator and the condenser of the water chilling unit, the throttle valve is arranged on the throttle pipe, the minimum pressure protection valve is arranged on the blowdown pipe, and the pressure of the evaporator is supplemented through the pressure difference between the evaporator and the condenser; therefore, frequent jump stop of the compressor caused by too low pressure of the evaporator can be avoided, damage to the compressor is avoided, and efficient, energy-saving and environment-friendly operation of the water chilling unit is guaranteed.

Description

Technical Field

[0001] The utility model relates to the technical field of chemical production, and in particular to an industrial centrifugal chiller capable of achieving minimum pressure protection for an evaporator. Background Art

[0002] In the chemical production process, the 5℃ water cooling system mainly uses centrifugal chillers for cooling. Centrifugal chillers are large-scale equipment that uses high-speed rotating centrifugal compressors for refrigeration. They are mainly used in air-conditioning systems in industry, commerce and large buildings to provide cooling water to meet the needs of air conditioning and process cooling. Its working process mainly includes the following steps:

[0003] Evaporation process: The refrigerant absorbs heat from the outside in the evaporator and evaporates into low-temperature and low-pressure steam;

[0004] Compression process: The evaporated refrigerant vapor enters the centrifugal compressor, and the high-speed rotation of the impeller compresses the refrigerant vapor into high-pressure and high-temperature gas;

[0005] Condensation process: High-pressure and high-temperature refrigerant gas releases heat in the condenser and is carried away by cooling water, turning into high-pressure liquid;

[0006] Throttling process: The high-pressure liquid passes through a throttling device (such as an expansion valve or orifice plate) to reduce pressure and temperature, becoming a low-pressure, low-temperature liquid and steam mixture, which then enters the evaporator to absorb heat and evaporate again, completing the refrigeration cycle.

[0007] During operation, a series of interlocks are set up between the PLC control system and the compressor, ensuring automatic shutdown in the event of a fault and automatic restart after recovery. However, the following issues often arise during operation: Unstable heat absorption from the chemical plant by the chilled water in the evaporator tubes, or seasonal temperature fluctuations in northern China, leads to unstable refrigerant evaporation in the shell side of the chiller's evaporator, resulting in low evaporator pressure. When the evaporator pressure is too low, the compressor suction pressure cannot be guaranteed. To prevent damage to the compressor, the PLC control program frequently trips the compressor. Once the evaporator pressure returns to normal (evaporator pressure ≥ 250 kPa for 15 minutes), the compressor restarts. Frequent compressor startups can cause a series of problems in the chiller, including wear and tear of motor and mechanical components, reduced equipment stability, compressor efficiency, system pressure fluctuations, and sealing system failure. This also poses a potential risk of accidents. Furthermore, frequent startups and shutdowns can trigger a series of interlocking reactions, such as lubrication failure, mechanical component seizure, and electrical equipment overheating, increasing the risk of serious equipment failures. Utility Model Content

[0008] The purpose of this utility model is to provide an industrial centrifugal chiller that can achieve minimum evaporator pressure protection, so as to solve the technical problem that the evaporator pressure of the existing centrifugal chiller is too low, resulting in the compressor suction pressure cannot be guaranteed and frequent starting and stopping are required, thereby causing equipment accidents or production accidents.

[0009] To achieve its purpose, the utility model adopts the following technical solutions:

[0010] An industrial centrifugal chiller capable of achieving minimum evaporator pressure protection comprises an evaporator, a condenser and a compressor;

[0011] The evaporator and condenser are horizontal shell-and-tube heat exchangers with the same structure and are arranged in parallel in the longitudinal direction. A pressure gauge is provided on the evaporator. The evaporator tube-side inlet is connected to the chilled water pipe outlet, and the tube-side outlet is connected to the chemical device to be cooled; the evaporator shell-side outlet is connected to the centrifugal compressor inlet, and a compressor suction valve is provided between the evaporator shell-side outlet and the centrifugal compressor inlet. The centrifugal compressor outlet is connected to the condenser shell-side inlet, and the condenser shell-side outlet is connected to the evaporator shell-side inlet through a throttle tube, and the throttle tube is provided with a throttle valve; the top of the condenser shell-side is also connected to the air supply pipe inlet, and the air supply pipe outlet is connected to the top of the evaporator shell-side, and a minimum pressure protection valve is provided on the air supply pipe; the condenser tube-side inlet is connected to the cooling water pipe, and the condenser tube-side outlet is connected to the hot water pipe;

[0012] The minimum pressure protection valve forms a pressure interlock with the unit PLC controller and the evaporator pressure gauge; the PLC controller forms an interlock with the minimum pressure protection valve, the compressor, and the compressor suction valve to provide shutdown protection for the unit's evaporator pressure being too low.

[0013] As a further improvement of the technical solution of the present invention, the shell side outlet of the evaporator is connected to the inlet of the centrifugal compressor through the compressor suction pipe, and a compressor suction valve is provided on the compressor suction pipe.

[0014] Furthermore, the inlets of the chilled water pipe and the cooling water pipe are respectively connected to the delivery pump, and the water source is provided by the delivery pump.

[0015] Furthermore, the compressor is a centrifugal compressor.

[0016] Furthermore, metal spiral wound gaskets are provided at the pipe flange connections in the unit.

[0017] Furthermore, the tubes in the shell-and-tube heat exchanger are made of copper alloy.

[0018] By adopting the above technical solution, the beneficial effects achieved by the utility model are as follows:

[0019] The heat absorption of the cold water in the evaporator tube of the chiller by the chemical device is unstable or affected by seasonal temperatures in northern China, resulting in unstable refrigerant evaporation in the shell of the chiller evaporator. This often leads to low evaporator pressure. When the evaporator pressure is too low, the compressor suction pressure cannot be guaranteed. To avoid damage to the compressor, the PLC control program will cause the compressor to frequently trip and stop. After the evaporator pressure returns to normal (evaporator pressure ≥ 250kPa for 15 minutes), the compressor will restart. The present invention uses a PLC control system to set a throttle tube and an air supply tube between the evaporator and condenser of the chiller, and a throttle valve is set on the throttle tube. A minimum pressure protection valve is set on the air supply tube. The evaporator pressure is supplemented by the pressure difference between the evaporator and the condenser. This can avoid frequent compressor trips and stops caused by low evaporator pressure, avoid damage to the compressor, and ensure that the chiller can operate efficiently, energy-saving, and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structure of an industrial centrifugal chiller capable of achieving minimum evaporator pressure protection according to the utility model;

[0021] Figure markings: 1-evaporator; 2-condenser; 3-compressor; 4-compressor suction pipe; 5-compressor suction valve; 6-compressor exhaust pipe; 7-throttle pipe; 8-throttle valve; 9-air supply pipe; 10-minimum pressure protection valve; 11-chilled water; 12-cooling water; 13-PLC controller; 14, hot water pipe; 15, pressure gauge. DETAILED DESCRIPTION

[0022] The structure and working process of the present invention are described in detail below with reference to the accompanying drawings.

[0023] Reference Figure 1The utility model provides an industrial centrifugal chiller capable of realizing minimum pressure protection of the evaporator, comprising an evaporator 1, a condenser 2 and a compressor 3; the evaporator 1 and the condenser 2 are horizontal shell-and-tube heat exchangers of the same structure and are arranged in parallel in the longitudinal direction; a pressure gauge 15 is provided on the evaporator 1; the tube-side inlet of the evaporator 1 is connected to the outlet of the chilled water pipe 11, and the tube-side outlet is connected to the chemical device to be cooled; the shell-side outlet of the evaporator 1 is connected to the inlet of the centrifugal compressor 3 through the compressor suction pipe 4, and the compressor suction pipe 4 is connected to the inlet of the centrifugal compressor 3. 4 is provided with a compressor suction valve 5, the outlet of the centrifugal compressor 3 is connected to the shell side inlet of the condenser 2, and the shell side outlet of the condenser 2 is connected to the shell side inlet of the evaporator 1 through a throttle tube 7, and the throttle tube 7 is provided with a throttle valve 8; the top of the shell side of the condenser 2 is also connected to the inlet of the air supply pipe 9, and the outlet of the air supply pipe 9 is connected to the top of the shell side of the evaporator 1, and the air supply pipe 9 is provided with a minimum pressure protection valve 10; the tube side inlet of the condenser 2 is connected to the cooling water pipe 12, and the tube side outlet of the condenser 2 is connected to the hot water pipe 14;

[0024] The minimum pressure protection valve 10 forms a pressure interlock with the unit PLC controller 13 and the pressure gauge of the evaporator 1; the PLC controller 13 forms an interlock with the minimum pressure protection valve 10, the compressor 3, and the compressor suction valve 4.

[0025] Specifically, the evaporator 1 is a shell and tube heat exchanger. The shell of the evaporator can be made of corrosion-resistant materials such as stainless steel, copper or aluminum alloy. A flow channel is designed inside the tube side to accommodate the heat exchange tube bundle. Multiple groups of parallel heat exchange tubes are designed. The tube bundle is composed of several slender tubes. Chilled water 11 flows through the tubes, and heat exchange is carried out outside the tubes through the refrigerant. The refrigerant absorbs a large amount of heat released by the chilled water 11 in the tube, and its own temperature rises. The refrigerant absorbs heat and evaporates in the shell side of the heat exchanger, changing from liquid to gas.

[0026] The condenser 2 has the same design and equipment structure as the evaporator 1. Its main function is to perform heat exchange between the refrigerant and the cooling water 12. The cooling water 12 flows through the heat exchange tubes, absorbs the heat released when the refrigerant outside the tubes condenses, and its own temperature rises. The refrigerant releases heat and condenses in the shell side of the heat exchanger, changing from gas to liquid.

[0027] The compressor 3 is a centrifugal compressor. A compressor suction pipe 4 and a compressor suction valve 5 are provided at the inlet of the compressor 3, and the other side is connected to the top of the shell side of the evaporator 1. A compressor exhaust pipe 6 is provided at the outlet of the compressor 3 and connected to the top of the condenser 2. The centrifugal compressor 3 obtains kinetic energy through the high-speed rotation of the impeller, and diffuses outward under the action of centrifugal force, thereby increasing the pressure and completing the gas compression process.

[0028] A throttle tube 7 is provided at the bottom of the shell side of the condenser 2, and a throttle valve 8 is provided on the throttle tube 7. The other side of the throttle tube 7 is connected to the bottom of the shell side of the evaporator 1. Its basic function is to limit the flow area of ​​the refrigerant so that the high-pressure liquid refrigerant will produce a pressure drop when flowing through the throttle valve 8. After the high-pressure liquid refrigerant coming out of the condenser 2 passes through the throttle valve 8, the pressure is significantly reduced, creating conditions for subsequent heat absorption and evaporation in the evaporator 1.

[0029] The air supply pipe 9 runs from the top of the shell side of the condenser 2 to the top of the shell side of the evaporator 1. A minimum pressure protection valve 10 is set on the air supply pipe 9. The minimum pressure protection valve 10 is pressure interlocked with the unit PLC controller 13 and the pressure gauge 15 of the evaporator 1. When the pressure of the evaporator 1 is low (displayed by the pressure gauge 15) (<200kPa), the PLC controller 13 controls the minimum pressure protection valve 10 to open, and the high-pressure refrigerant in the condenser 2 is transported to the evaporator 1, so as to ensure the pressure stability of the evaporator 1 and avoid the compressor 3 from tripping.

[0030] An interlock is set between the PLC controller 13 and the minimum pressure protection valve 10, the pressure gauge 15 of the compressor 3, and the compressor suction valve 5. The interlock logic is as follows: when the pressure of the pressure gauge 15 is ≤180kpa, the compressor suction valve 5 suspends action, and the minimum pressure protection valve 10 slowly opens to replenish pressure to the evaporator 1. When the pressure of the pressure gauge 15 is ≥250kpa, the minimum pressure protection valve 10 closes, and the compressor suction valve 5 starts suction adjustment to perform frequent tripping protection of the compressor 3.

[0031] The inlets of the chilled water pipe 11 and the cooling water pipe 12 are respectively connected to the delivery pump, and the water source is provided by the delivery pump. The chilled water and the cooling water continue to circulate after heat exchange through the evaporator 1 and the condenser 2 tubes respectively.

[0032] When the utility model is put into use, all pipes and fittings in the unit need to be pressure tested for leaks at a pressure of 1.5 MPa, and metal spiral wound gaskets are used to seal the pipe flange connections.

[0033] Furthermore, to ensure the accuracy of monitoring data, the pressure monitoring points of the evaporator 1 and the condenser 2 can use the pressure transmitter (instead of the pressure gauge 15) and PLC control program provided with the unit at the factory.

Claims

1. An industrial centrifugal chiller capable of achieving minimum evaporator pressure protection, comprising an evaporator (1), a condenser (2) and a compressor (3), characterized in that: The evaporator (1) and the condenser (2) are horizontal shell-and-tube heat exchangers with the same structure and are arranged in parallel in the longitudinal direction. A pressure gauge (15) is provided on the evaporator (1). The tube-side inlet of the evaporator (1) is connected to the outlet of the chilled water pipe (11), and the tube-side outlet is connected to the chemical device to be cooled. The shell-side outlet of the evaporator (1) is connected to the inlet of the centrifugal compressor (3), and a compressor suction valve (5) is provided between the shell-side outlet of the evaporator (1) and the inlet of the centrifugal compressor (3). The outlet of the centrifugal compressor (3) is connected to the condenser ( 2) the shell side inlet is connected, the shell side outlet of the condenser (2) is connected to the shell side inlet of the evaporator (1) through a throttling tube (7), and a throttling valve (8) is provided on the throttling tube (7); the top of the shell side of the condenser (2) is also connected to the inlet of the air supply pipe (9), and the outlet of the air supply pipe (9) is connected to the top of the shell side of the evaporator (1), and a minimum pressure protection valve (10) is provided on the air supply pipe (9); the tube side inlet of the condenser (2) is connected to the cooling water pipe (12), and the tube side outlet of the condenser (2) is connected to the hot water pipe (14); The minimum pressure protection valve (10) forms a pressure interlock with the unit PLC controller (13) and the pressure gauge (15) of the evaporator (1); an interlock is formed between the PLC controller (13) and the minimum pressure protection valve (10), the compressor (3), and the compressor suction valve (5), for shutdown protection in the event of excessively low evaporator pressure.

2. An industrial centrifugal chiller capable of achieving minimum evaporator pressure protection as claimed in claim 1, characterized in that: The shell side outlet of the evaporator (1) is connected to the inlet of the centrifugal compressor (3) through a compressor suction pipe (4), and a compressor suction valve (5) is provided on the compressor suction pipe (4).

3. The industrial centrifugal chiller capable of achieving minimum evaporator pressure protection according to claim 1, characterized in that: The inlets of the freezing water pipe (11) and the cooling water pipe (12) are respectively connected to the delivery pump, and the water source is provided by the delivery pump.

4. The industrial centrifugal chiller capable of achieving minimum evaporator pressure protection according to claim 1, characterized in that: The compressor (3) is a centrifugal compressor.

5. An industrial centrifugal chiller capable of achieving minimum evaporator pressure protection according to any one of claims 1 to 4, characterized in that: The pipe flange connections in the unit are all provided with metal spiral wound gaskets.

6. An industrial centrifugal chiller capable of achieving minimum evaporator pressure protection according to any one of claims 1 to 4, characterized in that: The tubes in the shell-and-tube heat exchanger are made of copper alloy.

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