CN108131854B - Direct expansion type liquid supply multi-parallel screw low-temperature water chilling unit - Google Patents
Direct expansion type liquid supply multi-parallel screw low-temperature water chilling unit Download PDFInfo
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- CN108131854B CN108131854B CN201810136322.7A CN201810136322A CN108131854B CN 108131854 B CN108131854 B CN 108131854B CN 201810136322 A CN201810136322 A CN 201810136322A CN 108131854 B CN108131854 B CN 108131854B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B1/00—Compression machines, plants or systems with non-reversible cycle
- F25B1/04—Compression machines, plants or systems with non-reversible cycle with compressor of rotary type
- F25B1/047—Compression machines, plants or systems with non-reversible cycle with compressor of rotary type of screw type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B41/00—Fluid-circulation arrangements
- F25B41/30—Expansion means; Dispositions thereof
- F25B41/31—Expansion valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
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Abstract
The invention discloses a direct expansion type liquid supply multi-parallel screw low-temperature water chilling unit, which comprises an exhaust condensing module, an economizer module, an evaporation module, an air return module and an oil circuit module, wherein the air return module and the oil circuit module form a closed refrigerant circulation loop and an oil circuit circulation loop; the economizer module is a single economizer and single expansion valve, so that the unit cost is low; the evaporation module is provided with a gas distribution tank, separating refrigerant steam after throttling expansion, the inlet of the evaporator is ensured to be uniformly distributed, and the energy efficiency of the unit is improved. The air return module is provided with the buffer tank, so that the risk of series leakage of the unit is reduced while the oil return of the unit is ensured, and the running reliability of the unit is improved.
Description
Technical Field
The invention belongs to in the field of refrigeration equipment, more particularly relates to the field of a direct expansion type liquid supply multi-parallel screw low-temperature water chilling unit.
Background
In recent years, the refrigeration industry rapidly develops, and the market proportion of water chilling units, particularly screw water chilling units, is gradually increased. From the product characteristics, the screw water chilling unit has extremely strong adaptability to projects, can be used for civilian use, commercial use and industry, and can also be used in combination with other types of units. From the application range, the screw water chiller can be used at high temperature, medium temperature and low Wen Duogong condition. In the prior art, the low-temperature water chilling unit, in particular to a multi-parallel screw low-temperature water chilling unit for direct expansion liquid supply, still has some defects.
The first, economizer module is complex and costly to manufacture.
The multi-parallel screw low-temperature chiller is generally provided with an economizer module for improving the operating energy efficiency of the compressor and reducing the exhaust temperature of the compressor. The prior method comprises the following steps: the number of the auxiliary parts of the multiple economizers and the multiple economizers, namely, the number of the economizers is consistent with the number of the compressors, so that the number of the parallel compressors of the unit is increased, the number of the auxiliary parts in the economizers and the economizer assemblies, such as a thermostatic expansion valve, an economizer electromagnetic valve and the like, is increased, and the unit cost is further increased. And secondly, the number of the single-economizer multi-economizer auxiliary parts is always one, namely, the number of accessories in the economizer auxiliary parts such as a thermal expansion valve and an economizer electromagnetic valve is determined according to the number of the compressors, an economizer return air is provided with a return air main pipe, the return air main pipe is divided into multiple paths to return to the economizer ports of the compressors, and the number of the economizers is one, but the number of the economizer auxiliary parts is also increased, so that the unit cost is increased. And thirdly, when the load of the refrigeration house is reduced, the energy adjustment of the compressor starts to be unloaded, and the load change cannot timely react to the economizer circuit, so that the superheat degree of the air return main pipe of the economizer is not timely changed, the expansion valve is not adjusted, and the liquid return of the compressor is easy to be caused.
And the heat exchange efficiency of the second evaporator can be improved.
The evaporator of the water chilling unit mainly comprises a dry evaporator, and an expansion valve is arranged at the inlet of the evaporator. After the refrigerant is throttled by the expansion valve, partial refrigerant steam can be generated, uneven liquid separation is easily caused when the refrigerant enters the dry evaporator, and the heat exchange area of the evaporator cannot be effectively utilized.
Thirdly, the leakage problem of the condenser and the evaporator cannot be avoided due to the limitation of technical process conditions.
In order to reduce leakage risk, a water chiller is usually provided with a gas-liquid separator at the return air. In actual operation, when the unit leaks, water or coolant is often found inside the compressor. On one hand, the volume of the gas-liquid separator is insufficient, and on the other hand, an oil return hole is formed in the bottom of an air return pipe of the gas-liquid separator, and the oil return hole also causes water or secondary refrigerant deposited at the bottom to be sucked when the unit leaks during oil return.
Disclosure of Invention
The invention provides the direct expansion type liquid supply multi-parallel screw low-temperature water chilling unit with low production cost, high energy utilization rate and high reliability, which aims to avoid the defects in the prior art.
The invention adopts the following technical scheme for solving the technical problems:
the invention relates to a direct expansion type liquid supply multi-parallel screw low-temperature water chilling unit which is characterized in that: the unit comprises an exhaust condensing module, an economizer module, an evaporating module, a return air module and an oil way module to form a closed refrigerant circulation loop and an oil way circulation loop;
the exhaust condensing module is sequentially arranged at an outlet of the self-compressor according to the refrigerant flow direction: the device comprises a compressor, an oil separator, a condenser, a filter vat and a liquid viewing mirror, wherein the compressor is formed by connecting two or more screw compressors with adjustable fixed frequency bands in parallel, and the condenser adopts a water cooling, air cooling or evaporative cooling condensation mode;
the economizer module contains refrigerant main loop and refrigerant branch circuit, the export of refrigerant flow direction from the liquid mirror sets gradually in the refrigerant main loop: a liquid inlet pipe ball valve, an economizer high-pressure side inlet, an economizer high-pressure side outlet and a liquid outlet pipe ball valve; the refrigerant branch circuit is led out from an outlet of the liquid inlet pipe ball valve and is sequentially arranged as follows according to the refrigerant flow direction: the system comprises a branch liquid viewing mirror, an economizer branch electromagnetic valve, an electronic expansion valve, an economizer low-pressure side inlet, an economizer low-pressure side outlet and a medium-pressure return air main pipe, wherein a refrigerant in the medium-pressure return air main pipe is connected in parallel and sequentially passes through a medium-pressure return air branch one-way valve and a medium-pressure return air branch ball valve to be connected with an economizer interface of each compressor;
the economizer is a plate heat exchanger or a shell-and-tube heat exchanger, and the refrigerant in the main refrigerant loop exchanges heat with the refrigerant in the refrigerant bypass loop throttled by the electronic expansion valve in the economizer, so that the refrigerant in the main loop is supercooled, and the bypass refrigerant is evaporated;
the evaporation module is connected with a liquid outlet pipe ball valve of the economizer module through a liquid supply main pipe, and the evaporation module is sequentially arranged from an outlet of the liquid outlet pipe ball valve according to the flow direction of a refrigerant: the device comprises a main pipe electromagnetic valve, a thermal expansion valve, a gas distribution tank inlet pipe, a gas distribution tank outlet pipe, a dry evaporator and an evaporator return pipe, wherein the gas distribution tank is used for separating refrigerant gas entrained in refrigerant liquid after being throttled by the thermal expansion valve, the liquid enters the dry evaporator through the gas distribution tank outlet pipe, and the gas enters the evaporator return pipe through the gas distribution tank outlet pipe;
the air return module is connected with an evaporator air return pipe through an inlet pipe of the buffer tank, an outlet pipe of the buffer tank is connected with an air return main pipe, and refrigerant liquid entrained in refrigerant in the evaporator air return pipe is separated by the buffer tank; the bottom of the buffer tank is respectively provided with a buffer tank bottom bypass pipe, a heat exchange pipe and a buffer tank liquid viewing mirror, wherein the buffer tank bottom bypass pipe is connected with a low-pressure bypass pipe and is connected into an air return main pipe through a low-pressure bypass electromagnetic valve;
the oil circuit module separates the frozen oil in the refrigerant by utilizing an oil separator, and the frozen oil is divided into a frozen oil main circuit and a frozen oil bypass circuit according to the flow direction; the main circuit of the frozen oil flows according to the direction of an oil way the oil outlet of the self-oil separator is sequentially provided with: the oil separator comprises an oil outlet pipe, a buffer tank bottom heat exchange pipe inlet, a buffer tank bottom heat exchange pipe and an oil cooler oil inlet pipe; the refrigerating oil exchanges heat with the refrigerant liquid deposited at the bottom of the buffer tank in the heat exchange tube at the bottom of the buffer tank, so that the temperature of the refrigerating oil is reduced, and the refrigerant liquid is evaporated; the refrigerating oil bypass loop is a bypass oil path led out from an oil outlet pipe of the oil separator, and is connected to an oil inlet pipe of the oil cooler, and an oil path bypass electromagnetic valve is arranged on the bypass oil path.
The direct expansion type liquid supply multi-parallel screw low-temperature water chilling unit is also characterized in that: the opening of the electronic expansion valve is controlled according to the superheat degree of the refrigerant gas in the medium-pressure return air main pipe and the adjustable change of the running compressor in the following mode:
detecting and obtaining the refrigerant temperature T31 in the medium-pressure air return main pipe by a temperature sensor, detecting and obtaining the pressure of the refrigerant in the medium-pressure air return main pipe by a low-pressure sensor, processing by a controller according to the pressure of the refrigerant in the medium-pressure air return main pipe to obtain a corresponding refrigerant saturation temperature T32, and setting the superheat degree of the refrigerant in the medium-pressure air return main pipe to be T0;
if T31-T32> T0, increasing the opening of the electronic expansion valve until t31=t32, and stopping the electronic expansion valve;
if T31-T32 is less than T0, decreasing the opening of the electronic expansion valve until t31=t32, and stopping the electronic expansion valve;
the method comprises the steps that the current opening preset value of an electronic expansion valve is set to be S1, the opening preset value after the electronic expansion valve is changed is set to be S2, the current adjustable state of the multi-parallel screw low-temperature water chilling unit is set to be R1%, the adjustable state after the change is set to be R2%, and the running state of the multi-parallel screw low-temperature water chilling unit with direct expansion is judged;
if the electronic expansion valve is in a loading state, the opening preset value of the electronic expansion valve is unchanged, namely S2=S1;
and if the electronic expansion valve is in an unloading state, the opening degree of the electronic expansion valve is preset to be S2=R2/R1×S1.
The direct expansion type liquid supply multi-parallel screw low-temperature water chilling unit is also characterized in that: the tank body height of the gas separation tank is higher than the inlet height of the dry evaporator, so that the refrigerant liquid overcomes the flow resistance in the heat exchange tube of the dry evaporator.
The direct expansion type liquid supply multi-parallel screw low-temperature water chilling unit is also characterized in that: a high liquid level switch and a low liquid level switch are respectively arranged on the side wall of the buffer tank, and the high liquid level switch is positioned above the low liquid level switch;
the compressor is controlled according to the liquid level in the buffer tank as follows: if the liquid level in the buffer tank is higher than the high liquid level switch, outputting a high liquid level alarm signal to the controller by using the high liquid level switch, and outputting a compressor alarm stop signal by the controller to stop the compressor in an alarm way;
the bypass electromagnetic valve is controlled according to the liquid level in the buffer tank and the state of the buffer tank liquid-viewing mirror in the following mode: if the liquid level in the buffer tank is lower than the low liquid level switch, outputting a low liquid level alarm signal to the controller by using the low liquid level switch, and if the state of the buffer tank liquid-viewing mirror is dry, opening a bypass electromagnetic valve; and otherwise, the bypass electromagnetic valve is kept to be closed, so that the compressor returns oil normally.
The direct expansion type liquid supply multi-parallel screw low-temperature water chilling unit is also characterized in that: the oil bypass solenoid valve is controlled according to a temperature signal of an oil inlet pipe of the oil cooler, so that when the temperature of frozen oil in the oil inlet pipe of the oil cooler is lower than a set value, the oil bypass solenoid valve is opened, and otherwise, the oil bypass solenoid valve is kept closed.
Compared with the prior art, the invention has the beneficial effects that:
1. the economizer module adopts the single-economizer single-electronic expansion valve, has low production cost and small occupied space, and is suitable for large-scale multi-parallel low-temperature water chilling units.
2. According to the invention, the electronic expansion valve is controlled by the superheat degree of the medium-pressure return air main pipe of the economizer and the adjustment and change of the compressor, so that the delay of the opening change of the electronic expansion valve caused by the adjustment and change of the unit is solved, and the risk of liquid return of the compressor is reduced.
3. According to the invention, the evaporation module is provided with the gas separation tank, so that the refrigerant vapor and the refrigerant liquid throttled by the expansion valve are separated, the inlet of the evaporator is ensured to be the refrigerant liquid, the liquid in the evaporator is more uniform, and the heat exchange area is effectively utilized.
4. The air return module is a buffer tank, the high liquid level switch arranged on the buffer tank controls the compressor to alarm and stop, so that the risk of internal leakage of the evaporator of the water chilling unit is effectively reduced, one path is led out from the bottom of the buffer tank, the low-pressure bypass electromagnetic valve is arranged, and the low-pressure bypass electromagnetic valve is controlled to start and stop by a button on a configuration interface according to the states of the low liquid level switch and the liquid viewing mirror, so that the unit can return oil normally, and the hidden trouble that the bypass channel sucks the secondary refrigerant when the evaporator leaks in a small amount is solved.
5. The high-temperature frozen oil separated by the oil separator exchanges heat with the liquid deposited at the bottom of the buffer tank through the heat exchange tube at the bottom of the buffer tank. The high-temperature frozen oil temperature is reduced, and the refrigerant in the liquid at the bottom of the buffer tank is evaporated, so that the energy efficiency of the unit is effectively improved. The oil way is provided with a bypass and controls the opening and closing of the oil bypass electromagnetic valve according to the oil temperature of the inlet pipe of the oil cooler, so that the risk of too low oil return temperature of the compressor is avoided.
Drawings
FIG. 1 is a schematic diagram of a system architecture of the present invention;
FIG. 2 is a schematic diagram of an economizer interface in the system of the present invention;
FIG. 3 is a schematic diagram of a vapor separation canister interface in the system of the present invention;
FIG. 4 is a schematic diagram of a buffer tank structure in the system of the present invention;
reference numerals in the drawings: 1 compressor, 2 oil separator, 3 condenser, 4 filter vat, 5 view mirror, 6 inlet pipe ball valve, 7 economizer, 71 economizer high pressure side inlet, 72 economizer high pressure side outlet, 73 economizer low pressure side inlet, 74 economizer low pressure side outlet, 8 branch view mirror, 9 economizer branch solenoid valve, 10 electronic expansion valve, 11 outlet pipe ball valve, 12 manifold solenoid valve, 13 thermal expansion valve, 14 branch gas tank, 141 branch gas tank inlet pipe, 142 branch gas tank outlet pipe, 143 branch gas tank outlet pipe, 15 dry evaporator, 16 buffer tank, 161 buffer tank view mirror, 162 heat exchange pipe, 163 high level switch, 164 low level switch, 165 buffer tank inlet pipe, 166 buffer tank outlet pipe, 167 buffer tank bottom bypass pipe, 168 buffer tank bottom heat exchange pipe inlet, 169 buffer tank bottom heat exchange pipe outlet, 17 oil bypass solenoid valve, 18 medium pressure return branch check valve, 19 medium pressure return branch ball valve, 20 low pressure bypass solenoid valve, 21 medium pressure return gas manifold, 22 supply manifold, 23 evaporator return gas pipe, 24 return gas pipe, 25 return gas pipe, 26 oil bypass oil cooler, 28 oil bypass oil separator.
Detailed Description
Referring to fig. 1, 2, 3 and 4, in the present embodiment, the direct expansion type multi-parallel screw low-temperature water chiller unit for liquid supply is a closed refrigerant circulation loop and an oil circulation loop formed by an exhaust condensing module, an economizer module, an evaporating module, an air return module and an oil circuit module.
The exhaust condensing module is sequentially arranged from an outlet of the compressor 1 according to the refrigerant flow direction: the compressor 1 is formed by connecting two or more screw compressors with adjustable fixed frequency bands in parallel, and the condenser 3 adopts a water cooling, air cooling or evaporative cooling condensation mode.
The economizer module contains refrigerant main loop and refrigerant branch circuit, and refrigerant main loop sets gradually according to the export of refrigerant flow direction from look liquid mirror 5: a feed pipe ball valve 6, an economizer high pressure side inlet 71, an economizer 7, an economizer high pressure side outlet 72 and a drain pipe ball valve 11; the refrigerant branch circuit is led out from the outlet of the liquid inlet pipe ball valve 6 and is sequentially arranged as follows according to the refrigerant flow direction: the bypass liquid-viewing mirror 8, the economizer bypass electromagnetic valve 9, the electronic expansion valve 10, the economizer low-pressure side inlet 73, the economizer 7, the economizer low-pressure side outlet 74 and the medium-pressure return air main pipe 21, wherein the refrigerant in the medium-pressure return air main pipe 21 is connected in parallel and sequentially passes through the medium-pressure return air bypass check valve 18 and the medium-pressure return air bypass ball valve 19 to be connected to the economizer interfaces of the compressors; the economizer 7 is a plate heat exchanger or a shell-and-tube heat exchanger, and the refrigerant in the main refrigerant loop exchanges heat with the refrigerant in the refrigerant bypass loop throttled by the electronic expansion valve 10 in the economizer 7, so that the refrigerant in the main loop is supercooled, and the bypass refrigerant is evaporated.
The evaporation module is connected with the liquid outlet pipe ball valve 11 of the economizer module through the liquid supply main pipe 22, and the evaporation module is sequentially arranged from the outlet of the liquid outlet pipe ball valve 11 according to the flow direction of the refrigerant: the main pipe electromagnetic valve 12, the thermal expansion valve 13, the gas-separating tank inlet pipe 141, the gas-separating tank 14, the gas-separating tank outlet pipe 142, the dry evaporator 15 and the evaporator muffler 23, the gas-separating tank 14 is utilized to separate the refrigerant gas carried in the refrigerant liquid throttled by the thermal expansion valve 13, the liquid enters the dry evaporator 15 through the gas-separating tank outlet pipe 142, and the gas enters the evaporator muffler 23 through the gas-separating tank outlet pipe 143.
The air return module is connected with the evaporator air return pipe 23 through a buffer tank inlet pipe 165, a buffer tank outlet pipe 166 is connected with the air return main pipe 24, and refrigerant liquid carried in the refrigerant in the evaporator air return pipe 23 is separated by the buffer tank 16; a buffer tank bottom bypass pipe 167, a heat exchange pipe 162 and a buffer tank liquid viewing mirror 161 are respectively arranged at the bottom of the buffer tank 16, and the buffer tank bottom bypass pipe 167 is connected with a low-pressure bypass pipe 25 and is connected into the return air main pipe 24 through a low-pressure bypass electromagnetic valve 20.
The oil circuit module separates the frozen oil in the refrigerant by utilizing the oil separator 2, and the frozen oil is divided into a frozen oil main circuit and a frozen oil bypass circuit according to the flow direction; the main circuit of the refrigerating oil is sequentially arranged from the oil outlet of the oil separator 2 according to the flow direction of the oil way: the oil separator oil outlet pipe 28, the buffer tank bottom heat exchange pipe inlet 168, the buffer tank bottom heat exchange pipe 162 and the buffer tank bottom heat exchange pipe outlet 169 are connected to the oil cooler oil inlet pipe 26; the frozen oil exchanges heat with the refrigerant liquid deposited at the bottom of the buffer tank in the heat exchange tube 162 at the bottom of the buffer tank, so that the temperature of the frozen oil is reduced, and the refrigerant liquid is evaporated; the refrigerating oil bypass circuit is a bypass oil path 27 led out from an oil outlet pipe 28 of the oil separator, and is connected to an oil inlet pipe 26 of the oil cooler, and an oil path bypass electromagnetic valve 17 is arranged on the bypass oil path 27.
The evaporation module in this embodiment employs a single economizer, package, and reduces the cost of the unit as compared to multiple economizer, multiple economizer packages.
The opening degree of the electronic expansion valve 10 is set in the present embodiment according to the degree of superheat of the refrigerant gas in the medium-pressure return air main 21 and the change in the capacity of the operating compressor as follows:
the temperature sensor detects and obtains the refrigerant temperature T31 in the medium-pressure air return main pipe 21, the unit is the temperature, the low-pressure sensor detects and obtains the pressure of the refrigerant in the medium-pressure air return main pipe 21, the controller processes and obtains the corresponding refrigerant saturation temperature T32 according to the refrigerant pressure in the medium-pressure air return main pipe 21, the unit is the temperature, the superheat degree of the refrigerant in the medium-pressure air return main pipe 21 is set to be T0, and the unit is the temperature.
If T31-T32> T0, the opening degree of the electronic expansion valve 10 is increased until t31=t32, and the electronic expansion valve 10 stops operating; if T31-T32< T0, the opening degree of the electronic expansion valve 10 is reduced, until t31=t32, the electronic expansion valve 10 stops operating.
The current opening preset value of the electronic expansion valve 10 is set as S1, the opening preset value after the change of the electronic expansion valve 10 is set as S2, the current adjustable state of the multi-parallel screw low-temperature water chilling unit is set as R1%, the adjustable state after the change is set as R2%, and the running state of the multi-parallel screw low-temperature water chilling unit with direct expansion is judged: if the electronic expansion valve 10 is in the loading state, the opening preset value of the electronic expansion valve 10 is unchanged, namely s2=s1; if the electronic expansion valve 10 is in the unloaded state, the opening degree is set to s2=r2/r1×s1.
Such as: setting the superheat degree of the refrigerant in the medium-pressure air return main pipe 21 to be 5 ℃, setting the pressure of the refrigerant in the medium-pressure air return main pipe 21 to be 0.53MPa, setting the corresponding saturation temperature T32 of the refrigerant to be 2 ℃, and increasing the opening of the electronic expansion valve 10 if T31 is 8 ℃, until the electronic expansion valve 10 stops acting when T31 = T32; if T31 is 5 ℃, the opening degree of the electronic expansion valve 10 is reduced, and when t31=t32, the electronic expansion valve 10 stops operating.
The current opening preset value of the electronic expansion valve 10 is set to 2000 steps, the opening preset value after the electronic expansion valve 10 is changed is set to S2, the current adjustable state of the multi-parallel screw low-temperature water chilling unit is set to 100%, the adjustable state after the change is set to 50%, and the running state of the multi-parallel screw low-temperature water chilling unit with direct expansion is judged: if the valve is in the loading state, the opening preset value of the electronic expansion valve 10 is unchanged, namely s2=s1=2000; if the valve is in the unloading state, the opening degree of the electronic expansion valve 10 is preset to s2=100/50×2000=1000.
As shown in fig. 3, in this embodiment, the volume of the gas separation tank 14 is calculated according to the volume of the effective liquid in the dry evaporator 15 in the safe time, and the gas separation tank gas inlet pipe 141 is located at the upper portion of the gas separation tank sidewall and at a certain distance from the gas separation tank gas outlet pipe 143, so as to ensure the effective separation of the refrigerant liquid and the refrigerant gas. The liquid outlet pipe 142 of the gas separation tank is positioned at the bottom of the gas separation tank to ensure liquid supply.
In the embodiment, the tank body height of the gas separation tank 14 is higher than the inlet height of the dry evaporator 15, so that the refrigerant liquid overcomes the flow resistance in the heat exchange tube of the dry evaporator 15, and the gas separation tank 14 and the inlet of the dry evaporator 15 have a height difference, so that on one hand, the heat exchange efficiency of the evaporator can be improved; on the other hand, the refrigerant can be prevented from directly flowing out from the gas outlet pipe 143 of the gas separation tank.
As shown in fig. 4, in the embodiment, the refrigerant in the evaporator air return pipe 23 enters the buffer tank 16, the refrigerant gas entrained in the refrigerant is separated by utilizing the steering and flow velocity change of the refrigerant, and a high liquid level switch 163 and a low liquid level switch 164 are respectively arranged on the side wall of the buffer tank 16, wherein the high liquid level switch 163 is positioned above the low liquid level switch 164.
The compressor 1 is controlled according to the liquid level in the buffer tank 16 as follows: if the liquid level in the buffer tank 16 is higher than the high liquid level switch 163, the high liquid level switch 163 is utilized to output a high liquid level alarm signal to the controller, and the controller outputs a compressor alarm stop signal to stop the compressor 1 in an alarm way.
In this embodiment, the buffer tank 16 separates refrigerant liquid and carries refrigerant oil dissolved in the refrigerant liquid, so a bypass solenoid valve 20 is provided, and the low-pressure bypass pipe 25 is controlled to be connected and closed according to the bypass solenoid valve 20, so as to ensure oil return. The bypass solenoid valve 20 is controlled in accordance with the liquid level in the buffer tank 16 and the state of the buffer tank liquid mirror 161 as follows: if the liquid level in the buffer tank 16 is lower than the low liquid level switch 164, outputting a low liquid level alarm signal to the controller by utilizing the low liquid level switch 164, projecting the state of the buffer tank liquid viewing mirror 161 to a central control room by a field installation projection device, and if the state of the central control observation buffer tank liquid viewing mirror 161 is dry, opening the bypass electromagnetic valve 20; conversely, the bypass solenoid valve 20 is kept closed, so that the compressor 1 returns normally.
The oil bypass solenoid valve 17 in this embodiment is controlled in accordance with the temperature signal of the oil cooler oil inlet pipe 26 such that when the temperature of the frozen oil in the oil cooler oil inlet pipe 26 is lower than a set value, the oil bypass solenoid valve 17 is opened, whereas the oil bypass solenoid valve 17 is kept closed. If the set temperature of the frozen oil in the oil inlet pipe 26 of the oil cooler is 70 ℃, when the actual oil temperature is lower than 70 ℃, the oil bypass electromagnetic valve 17 is opened, otherwise, the oil bypass electromagnetic valve 17 is closed, and the oil return temperature of the compressor is controlled.
Claims (4)
1. A direct expansion type liquid supply multi-parallel screw low-temperature water chilling unit is characterized in that: the unit comprises an exhaust condensing module, an economizer module, an evaporating module, a return air module and an oil way module to form a closed refrigerant circulation loop and an oil way circulation loop;
the exhaust condensing module is sequentially arranged at an outlet of the self-compressor (1) according to the refrigerant flow direction: the device comprises a compressor (1), an oil separator (2), a condenser (3), a filter vat (4) and a liquid viewing mirror (5), wherein the compressor (1) is formed by connecting two or more screw compressors with adjustable fixed frequency bands in parallel, and the condenser (3) adopts a water cooling, air cooling or evaporative cooling condensation mode;
the economizer module contains refrigerant main loop and refrigerant branch circuit, the export that refrigerant main loop was looked from liquid mirror (5) according to refrigerant flow direction sets gradually: a liquid inlet pipe ball valve (6), an economizer high-pressure side inlet (71), an economizer (7), an economizer high-pressure side outlet (72) and a liquid outlet pipe ball valve (11); the refrigerant branch circuit is led out from an outlet of the liquid inlet pipe ball valve (6), and is sequentially arranged as follows according to the refrigerant flow direction: the system comprises a branch liquid viewing mirror (8), an economizer branch electromagnetic valve (9), an electronic expansion valve (10), an economizer low-pressure side inlet (73), an economizer (7), an economizer low-pressure side outlet (74) and a medium-pressure return air main pipe (21), wherein the medium in the medium-pressure return air main pipe (21) is connected into an economizer interface of each compressor in parallel and sequentially passes through a medium-pressure return air branch one-way valve (18) and a medium-pressure return air branch ball valve (19);
the economizer (7) is a plate heat exchanger or a shell-and-tube heat exchanger, and the refrigerant in the main refrigerant loop exchanges heat with the refrigerant in the refrigerant branch loop throttled by the electronic expansion valve (10) in the economizer (7) to supercool the refrigerant in the main loop and evaporate the branch refrigerant;
the evaporation module is connected with a liquid outlet pipe ball valve (11) of the economizer module through a liquid supply main pipe (22), and the evaporation module is sequentially arranged from an outlet of the liquid outlet pipe ball valve (11) according to the flow direction of a refrigerant: the device comprises a main pipe electromagnetic valve (12), a thermal expansion valve (13), a gas distribution tank inlet pipe (141), a gas distribution tank (14), a gas distribution tank outlet pipe (142), a dry evaporator (15) and an evaporator return pipe (23), wherein the gas distribution tank (14) is used for separating refrigerant gas carried in refrigerant liquid after being throttled by the thermal expansion valve (13), the liquid enters the dry evaporator (15) through the gas distribution tank outlet pipe (142), and the gas enters the evaporator return pipe (23) through a gas distribution tank outlet pipe (143);
the air return module is connected with the evaporator air return pipe (23) through a buffer tank inlet pipe (165), an outlet pipe (166) of the buffer tank is connected with the air return main pipe (24), and refrigerant liquid carried in the refrigerant in the evaporator air return pipe (23) is separated by the buffer tank (16); a buffer tank bottom bypass pipe (167), a heat exchange pipe (162) and a buffer tank liquid viewing mirror (161) are respectively arranged at the bottom of the buffer tank (16), and the buffer tank bottom bypass pipe (167) is connected with a low-pressure bypass pipe (25) and is connected into an air return main pipe (24) through a low-pressure bypass electromagnetic valve (20);
the oil circuit module utilizes an oil separator (2) to separate the frozen oil in the refrigerant, and the frozen oil is divided into a frozen oil main circuit and a frozen oil bypass circuit according to the flow direction; the main circuit of the frozen oil is sequentially arranged from an oil outlet of the oil separator (2) according to the flow direction of an oil way: the oil separator comprises an oil outlet pipe (28), a buffer tank bottom heat exchange pipe inlet (168), a buffer tank bottom heat exchange pipe (162) and a buffer tank bottom heat exchange pipe outlet (169) which are connected to an oil cooler oil inlet pipe (26); the refrigerating oil exchanges heat with the refrigerant liquid deposited at the bottom of the buffer tank in the heat exchange tube (162) at the bottom of the buffer tank, so that the temperature of the refrigerating oil is reduced, and the refrigerant liquid is evaporated; the refrigerating oil bypass loop is a bypass oil path (27) led out from an oil outlet pipe (28) of the oil separator and is connected to an oil inlet pipe (26) of the oil cooler, and an oil path bypass electromagnetic valve (17) is arranged on the bypass oil path (27);
the opening of the electronic expansion valve (10) is controlled according to the superheat degree of the cold gas in the medium-pressure return air main pipe (21) and the energy adjustment change of the running compressor as follows:
detecting and obtaining the refrigerant temperature T31 in the medium-pressure air return main pipe (21) by a temperature sensor, detecting and obtaining the pressure of the refrigerant in the medium-pressure air return main pipe (21) by a low-pressure sensor, processing by a controller according to the refrigerant pressure in the medium-pressure air return main pipe (21) to obtain the corresponding refrigerant saturation temperature T32, and setting the refrigerant superheat degree in the medium-pressure air return main pipe (21) to be T0;
if (T31-T32) > T0, the opening degree of the electronic expansion valve (10) is increased, and when T31 = T32, the electronic expansion valve (10) stops operating;
if (T31-T32) < T0, decreasing the opening of the electronic expansion valve (10) until T31 = T32, stopping the electronic expansion valve (10);
the method comprises the steps that a current opening preset value of an electronic expansion valve (10) is set to be S1, the opening preset value after the electronic expansion valve (10) is changed is set to be S2, the current adjustable state of the multi-parallel screw low-temperature water chilling unit is set to be R1%, the changed adjustable state is set to be R2%, and the running state of the direct expansion multi-parallel screw low-temperature water chilling unit is judged;
if the electronic expansion valve is in a loading state, the opening preset value of the electronic expansion valve (10) is unchanged, namely S2=S1;
and if the electronic expansion valve (10) is in an unloading state, the opening degree of the electronic expansion valve is preset to be S2=R2/R1×S1.
2. The direct expansion type liquid supply multi-parallel screw cryogenic water chilling unit according to claim 1, wherein the direct expansion type liquid supply multi-parallel screw cryogenic water chilling unit is characterized in that: the tank body height of the gas separation tank (14) is higher than the inlet height of the dry evaporator (15), so that the refrigerant liquid overcomes the flow resistance in the heat exchange tube of the dry evaporator (15).
3. The direct expansion type liquid supply multi-parallel screw cryogenic water chilling unit according to claim 1, wherein the direct expansion type liquid supply multi-parallel screw cryogenic water chilling unit is characterized in that: a high liquid level switch (163) and a low liquid level switch (164) are respectively arranged on the side wall of the buffer tank (16), and the high liquid level switch (163) is positioned above the low liquid level switch (164);
the compressor (1) is controlled in accordance with the liquid level in the buffer tank (16) in the following manner: if the liquid level in the buffer tank (16) is higher than the high liquid level switch (163), outputting a high liquid level alarm signal to the controller by using the high liquid level switch (163), and outputting a compressor alarm stop signal by the controller to ensure that the compressor (1) is in alarm stop;
the bypass solenoid valve (20) is controlled according to the liquid level in the buffer tank (16) and the state of the buffer tank liquid viewing mirror (161) as follows: if the liquid level in the buffer tank (16) is lower than a low liquid level switch (164), outputting a low liquid level alarm signal to a controller by using the low liquid level switch (164), and if the state of the buffer tank liquid viewing mirror (161) is observed to be dry, closing a bypass electromagnetic valve (20); otherwise, the bypass electromagnetic valve (20) is kept to be opened, so that the compressor (1) returns oil normally.
4. The direct expansion type liquid supply multi-parallel screw cryogenic water chilling unit according to claim 1, wherein the direct expansion type liquid supply multi-parallel screw cryogenic water chilling unit is characterized in that: the oil bypass solenoid valve (17) is controlled according to a temperature signal of the oil cooler oil inlet pipe (26) so that the oil bypass solenoid valve (17) is opened when the temperature of frozen oil in the oil cooler oil inlet pipe (26) is lower than a set value, and conversely, the oil bypass solenoid valve (17) is kept closed.
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| CN111928517A (en) * | 2020-08-18 | 2020-11-13 | 南京天加环境科技有限公司 | Multi-split air conditioning system based on double compressors and control method thereof |
| CN113091355B (en) * | 2021-04-16 | 2021-11-19 | 东北大学 | Heat pipe and vapor compression composite air conditioning system and method with uniform liquid distribution |
| CN115691294A (en) * | 2022-12-01 | 2023-02-03 | 渤海造船厂集团有限公司 | Acrylic composite refrigerator teaching device and application thereof |
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