CN111043783B - Self-cascade refrigeration system for trapping cryogenic water vapor and control method - Google Patents

Self-cascade refrigeration system for trapping cryogenic water vapor and control method Download PDF

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CN111043783B
CN111043783B CN201911378248.0A CN201911378248A CN111043783B CN 111043783 B CN111043783 B CN 111043783B CN 201911378248 A CN201911378248 A CN 201911378248A CN 111043783 B CN111043783 B CN 111043783B
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electromagnetic valve
low
temperature
evaporator
outlet
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CN111043783A (en
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王勤
张靖鹏
陈福胜
宋琦
罗介霖
赵朕
刘轶伦
陈光明
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Zhejiang University ZJU
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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
    • F25B7/00—Compression machines, plants or systems, with cascade operation, i.e. with two or more circuits, the heat from the condenser of one circuit being absorbed by the evaporator of the next circuit
    • 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
    • F25B33/00—Boilers; Analysers; Rectifiers
    • 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
    • F25B40/00—Subcoolers, desuperheaters or superheaters
    • F25B40/06—Superheaters
    • 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
    • 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
    • F25B43/00—Arrangements for separating or purifying gases or liquids; Arrangements for vaporising the residuum of liquid refrigerant, e.g. by heat
    • F25B43/02—Arrangements for separating or purifying gases or liquids; Arrangements for vaporising the residuum of liquid refrigerant, e.g. by heat for separating lubricants from the refrigerant

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  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Devices That Are Associated With Refrigeration Equipment (AREA)

Abstract

The invention discloses a self-cascade refrigeration system for trapping cryogenic water vapor, which comprises a compressor, an oil separator, a condenser, a rectification device, a high-temperature heat regenerator, a low-temperature heat regenerator, a standby pipeline, a cold accumulator pipeline, an evaporator and first to sixth electromagnetic valves which are connected through pipelines, wherein the top of the rectification device is provided with a kettle top heat exchanger; the evaporator, the standby pipeline and the cold accumulator pipeline which are connected in parallel form a working space; the self-cascade refrigeration system comprises three working modes of standby, refrigeration and defrosting, and the switching between the working modes is realized by a first solenoid valve, a second solenoid valve, a third solenoid valve, a fourth solenoid valve and a sixth solenoid valve. The self-cascade refrigeration system provided by the invention can ensure that the refrigerant and the evaporator coil have larger heat exchange temperature difference through switching the standby mode and the refrigeration mode, so that the evaporator obtains higher cooling speed. Meanwhile, due to the arrangement of the cold accumulator pipeline, the flow entering the evaporator is larger during switching, and the evaporator can obtain a higher cooling speed.

Description

Self-cascade refrigeration system for trapping cryogenic water vapor and control method
Technical Field
The invention relates to the technical field of refrigeration, low-temperature engineering and vacuum, in particular to a self-cascade refrigeration system for trapping cryogenic water vapor and a control method.
Background
A device that reduces the partial pressure of harmful components in a gas and vapor mixture by physical or chemical means is called a trap, a cryotrap is a trap that traps gases in a condensed manner on a cooled surface. The cryotrap is commonly used in the field of low-temperature medicine research, the application range is rapidly expanded in recent years, and the cryotrap is widely applied to the aspects of medicine production, petrochemical industry, biochemical experiments, high vacuum construction, oil-gas separation, reagent distillation and extraction, even nuclear industry and the like. The low-temperature cold trap mainly plays a role in capturing water vapor and separating oil stains in the construction of a high-vacuum environment.
The vacuum technology is used as a basic technology in a plurality of high and new technical fields such as information technology, material science and the like, and plays an important role in various fields of economic development and national defense reserve. With the rapid development of high and new technologies, the demand for high vacuum and ultra-high vacuum is increasing (vacuum degree is 10)-4～ 10-6Pa) is added. The research shows that: when the vacuum degree is higher than 10-4When Pa is needed, 65-95% of residual gas is water vapor. The existing vacuum pump (including molecular pump, diffusion pump, etc.) is difficult to effectively pump water vapor, and the pumping speed is low. When a vacuum environment is used, it is generally desirable to achieve the required vacuum level as quickly as possible, especially where the vacuum system is constantly on. Therefore, the method of using cryotrap condensation to capture water vapor has become the mainstream of creating a high vacuum environment.
One of the devices for trapping water vapor by using the low-temperature cold trap adopts a liquid nitrogen cold trap. However, this method is inconvenient due to the use of liquid nitrogen, especially in the absence of a supply of liquid nitrogen. Meanwhile, the cost of liquid nitrogen cooling is higher than that of the refrigeration of a common refrigerator, and the mode is not suitable for a system running for a long time, and is mainly adopted in short-term experiments in a laboratory in the past. In addition, a cryogenic water vapor trap adopting a mechanical refrigeration mode is developed at present. For example, the American IGC-Polycold company sees http: // www.igc.com/polycold/products /) provides an external Water Vapor trap and a Water Vapor trap (PFC Fast Cycle Water Vapor Cryopump) with a built-in condensing coil in a vacuum chamber, which is used for improving pumping speed and reducing Water Vapor residue in the vacuum chamber and is widely applied to occasions such as vacuum coating, semiconductor device production and the like. The main structure is that a refrigerator is adopted to cool the trapping surface arranged in the high vacuum system, so as to realize the trapping of water vapor in the high vacuum chamber and improve the performance of the high vacuum system.
The prior art of the united states IGC-Polycold company (US patent US5901558) reports a low-temperature water vapor cold trap adopting an integral gate valve structure, and a common high-vacuum system requires that a gate valve is adopted for separation between a vacuum chamber and a vacuum pump inlet.
The invention patent CN200410047936.6 reports a high vacuum cryogenic water vapor trap, wherein the low temperature fluid throttled by a refrigeration system sequentially passes through a low vacuum trapping unit and a high vacuum trapping unit; the high vacuum trapping unit is arranged in a high vacuum chamber, and the vacuum environment in the high vacuum chamber is built by a high vacuum pump; the low vacuum trapping unit is used for trapping water vapor in pipelines of the outlet of the high vacuum pump and the inlet of the backing stage vacuum pump, and can improve the performance of the high vacuum pump and the vacuum degree in the high vacuum chamber.
The trapping efficiency of the surface of the cold trap of the cryogenic water vapor trap is mainly determined by the temperature of the surface of the cold trap and the cooling speed, namely, effective measures for improving the efficiency of trapping water vapor on the surface of the cold trap are (1) constructing lower surface temperature; (2) and a faster cooling speed is achieved. However, no effective way for increasing the temperature reduction rate of the trapping device is reported at present.
Disclosure of Invention
In order to solve the technical problems, the invention provides a self-cascade refrigeration system for trapping cryogenic water vapor and a control method thereof, which can realize that a cryogenic water vapor trapping device achieves a faster cooling rate, thereby obtaining a faster trapping efficiency.
The invention provides the following technical scheme:
a self-cascade refrigeration system for trapping cryogenic water vapor comprises a compressor, an oil separator, a condenser, a rectification device, a high-temperature heat regenerator, a low-temperature heat regenerator, a cold accumulator and an evaporator which are connected through pipelines, wherein a kettle top heat exchanger is arranged at the top of the rectification device;
the exhaust port of the compressor is connected with the inlet of the oil separator;
the inlet of the condenser is connected with the outlet of the oil separator, and the outlet of the condenser is connected with the inlet of the rectifying device;
the kettle bottom outlet of the rectifying device is connected with the low-pressure side inlet of the high-temperature heat regenerator through a second throttle valve; the kettle top outlet of the rectifying device is connected with the high-pressure side inlet of the high-temperature heat regenerator; the outlet of the kettle top heat exchanger is connected with the air suction port of the compressor; the inlet of the kettle top heat exchanger is connected with the outlet of the low-pressure side of the high-temperature heat regenerator;
the high-pressure side outlet of the high-temperature regenerator is connected with the high-pressure side inlet of the low-temperature regenerator; the low-pressure side inlet of the high-temperature heat regenerator is connected with the low-pressure side outlet of the low-temperature heat regenerator;
the high-pressure side outlet of the low-temperature heat regenerator is connected with the inlet of the evaporator through a first throttling valve, and the connecting pipeline is a refrigerant inlet pipeline; the low-pressure side inlet of the low-temperature heat regenerator is connected with the outlet of the evaporator, and the connecting pipeline is a refrigerant outlet pipeline;
a first standby pipeline and a cold accumulator pipeline which are connected with the evaporator in parallel are sequentially arranged below the first throttle valve; the first standby pipeline is communicated with the refrigerant inlet pipeline and the refrigerant outlet pipeline, and a first electromagnetic valve is arranged on the first standby pipeline; an upper inlet and an upper outlet of the regenerator are respectively communicated to a refrigerant inlet pipeline and a refrigerant outlet pipeline through a regenerator pipeline, and a lower outlet of the regenerator is connected with an inlet of the evaporator; a second electromagnetic valve is arranged on a connecting pipeline between an upper inlet of the regenerator and a refrigerant inlet pipeline, a third electromagnetic valve is arranged on a connecting pipeline between an upper outlet of the regenerator and a refrigerant outlet pipeline, and a fifth electromagnetic valve is arranged on a connecting pipeline between a lower outlet of the regenerator and an inlet of the evaporator; a fourth electromagnetic valve is arranged on the refrigerant inlet pipeline;
a sixth electromagnetic valve and a third throttle valve are sequentially arranged between the outlet of the oil separator and the inlet of the evaporator;
the first standby pipeline, the cold accumulator and the evaporator form a working space.
The first electromagnetic valve, the second electromagnetic valve, the third electromagnetic valve, the fourth electromagnetic valve, the fifth electromagnetic valve and the sixth electromagnetic valve are all on-off electromagnetic valves.
The self-cascade refrigeration system adopts a multi-element mixed working medium, and the multi-element mixed working medium is a binary or multi-element mixed working medium selected from nitrogen, argon, alkane, olefin or halogenated hydrocarbon.
The self-cascade refrigeration system comprises the following working modes: the cold storage defrosting control system comprises a non-cold storage standby mode, a non-cold storage refrigerating mode, a non-cold storage defrosting mode and a cold storage defrosting mode, wherein the working modes are switched by a first electromagnetic valve and/or a second electromagnetic valve and/or a third electromagnetic valve and/or a fourth electromagnetic valve and/or a fifth electromagnetic valve and/or a sixth electromagnetic valve. The non-cold storage standby mode and the cold storage standby mode can be collectively called as a standby mode, the non-cold storage refrigeration mode and the cold storage refrigeration mode can be collectively called as a refrigeration mode, and the non-cold storage defrosting mode and the cold storage defrosting mode are collectively called as a defrosting mode.
In the self-cascade refrigeration system provided by the invention, in order to ensure the efficient operation of the system, the low-temperature cold trap refrigeration system is provided with three working modes of standby, refrigeration and defrosting, and the switching between the working modes is realized by a first electromagnetic valve to a sixth electromagnetic valve. The switching of the working modes is carried out in the working space. If the temperature reaches the low temperature behind the first throttle valve, the standby mode is switched to the refrigeration mode, and the low-temperature refrigerant flowing through the first standby pipeline enters the evaporator to cool the coil of the evaporator so as to achieve the use target. Compared with a mode that a low-temperature refrigerant of a common refrigeration system directly enters the evaporator for coil cooling after being started (namely, the refrigerant directly enters the refrigeration mode after being started), the standby mode is switched to the refrigeration mode, so that the refrigerant and the evaporator coil have larger heat exchange temperature difference, and the evaporator obtains higher cooling speed.
At the instant of switching between the two modes, the flow rate of the refrigerant does not change significantly. In order to further improve the cooling rate of the evaporator, a cold storage pipeline is connected in parallel with the first standby pipeline, part of low-temperature refrigerant in the standby mode is stored in the cold storage pipeline, and when the system is switched to the cooling mode, the part of refrigerant flows into the evaporator coil together with the refrigerant in the pipeline, so that the flow rate of the refrigerant can be increased at the initial stage of the cooling mode, and the cooling rate is accelerated. Therefore, the invention adds a cold accumulator to accelerate the cooling speed of the evaporator during the mode switching on the basis of the original rectification type self-cascade system. Thus, the operating modes of the cryotrap refrigeration system are increased as follows: the cold storage defrosting device comprises six working modes, namely a non-cold storage standby mode, a non-cold storage refrigerating mode, a non-cold storage defrosting mode and a cold storage defrosting mode.
Therefore, the switching from the standby mode to the cooling mode in the self-cascade refrigeration system provided by the invention can be switching from the non-cold storage standby mode to the non-cold storage refrigeration mode or switching from the cold storage standby mode to the cold storage refrigeration mode (with the participation of the cold storage device).
The invention also provides a control method of the self-cascade refrigeration system for trapping the cryogenic water vapor, which comprises the following steps:
non-cold storage standby mode: opening a first electromagnetic valve, closing a second electromagnetic valve, a third electromagnetic valve, a fourth electromagnetic valve, a fifth electromagnetic valve and a sixth electromagnetic valve, further throttling and cooling the low-temperature refrigerant by a first throttling valve, and enabling the low-temperature refrigerant to flow through the first electromagnetic valve and then enter a low-temperature heat regenerator;
non-cold storage refrigeration mode: in a non-cold storage standby mode, when the outlet of the first throttle valve reaches low temperature (set refrigeration temperature), closing the first electromagnetic valve, simultaneously opening the fourth electromagnetic valve, keeping the second electromagnetic valve, the third electromagnetic valve, the fifth electromagnetic valve and the sixth electromagnetic valve of the electromagnetic valves closed, and enabling a low-temperature refrigerant to flow through a coil pipe of the evaporator to provide cold energy of a cold trap and then enter a low-temperature heat regenerator;
non-cold storage defrosting mode: in a non-cold storage refrigeration mode, closing the fourth electromagnetic valve, opening the sixth electromagnetic valve, adjusting the opening degree of the third throttle valve, exhausting gas from a part of high-temperature compressor, entering a coil of the evaporator, raising the temperature of the evaporator coil to be above 0 ℃, completing the defrosting process of the evaporator coil, re-closing the sixth electromagnetic valve, and opening the fourth electromagnetic valve;
cold storage standby mode: opening a second electromagnetic valve and a third electromagnetic valve, closing the first electromagnetic valve, a fourth electromagnetic valve, a fifth electromagnetic valve and a sixth electromagnetic valve, further throttling and cooling the low-temperature refrigerant by a first throttle valve, allowing the low-temperature refrigerant to flow through the second electromagnetic valve to enter a regenerator, allowing part of the low-temperature refrigerant to accumulate in the regenerator, and allowing the other part of the refrigerant to flow through the third electromagnetic valve from an upper outlet of the regenerator to enter a low-temperature regenerator;
cold storage refrigeration mode: when the outlet of the first throttle valve reaches low temperature, the third electromagnetic valve is closed, the fourth electromagnetic valve and the fifth electromagnetic valve are opened, the first electromagnetic valve, the second electromagnetic valve, the third electromagnetic valve and the sixth electromagnetic valve are kept closed, and the low-temperature refrigerant accumulated in the cold accumulator enters a coil pipe of the evaporator along with the low-temperature refrigerant in the refrigerant inlet pipeline to provide cold energy of a cold trap and then enters a low-temperature heat regenerator;
cold accumulation defrosting mode: and in the cold storage refrigeration mode, closing the fourth electromagnetic valve and the fifth electromagnetic valve, opening the sixth electromagnetic valve, adjusting the opening degree of the third throttle valve, exhausting air from a part of the high-temperature compressor, entering a coil of the evaporator, raising the temperature of the coil of the evaporator to be above 0 ℃, completing the defrosting process of the coil of the evaporator, re-closing the sixth electromagnetic valve, and opening the fourth electromagnetic valve and the fifth electromagnetic valve.
The non-cold accumulation standby mode and the cold accumulation standby mode can realize the pre-cooling process of the refrigerating system and the recovery process of the unit, and prepare for capturing water vapor by the low-temperature coil pipe at any time. The low temperature coil is rapidly cooled to the desired lower temperature for moisture capture.
Wherein, the working process from the cascade refrigeration system does:
the multi-element mixed working medium is compressed by a compressor and then is changed into high-temperature and high-pressure gas, the high-temperature and high-pressure gas enters a rectifying device after being condensed by an oil separator and a condenser, after heat and mass exchange, a high-boiling component mixture is condensed in the rectifying device and separated from a low-boiling component mixture, the high-boiling component mixture flows out from an outlet at the bottom of the rectifying device, and the low-boiling component mixture participates in circulation from an outlet of a kettle top heat exchanger; the high-boiling component mixture enters a high-temperature heat regenerator for evaporation and heat absorption after being throttled and expanded by a second throttle valve, and cold energy is provided for the low-boiling component mixture subjected to heat exchange in the high-temperature heat regenerator; the evaporated high-boiling component mixture still has part of cold energy, flows through the kettle top heat exchanger and precools the low-boiling component mixture in the kettle top heat exchanger, and further enhances the separation effect of the rectifying device; the high-boiling component mixture enters an air suction port of the compressor and participates in circulation again;
the low-boiling component mixture rises and flows out in the rectifying device, and after the low-boiling component mixture is subjected to rectification and precooling by a kettle top heat exchanger, the high-boiling component mixture mixed in the low-boiling component mixture is separated; after precooling the low-boiling component mixture by the kettle top heat exchanger and the high-temperature heat regenerator, further cooling the low-boiling component mixture in the low-temperature heat regenerator by the evaporated low-boiling component mixture, and enabling the low-boiling component mixture to enter a working space as a low-temperature refrigerant after passing through a first throttling valve so as to provide cold energy for the working space; the low-boiling component mixture after heat exchange flows out of the working space and passes through the low-temperature heat regenerator, and then is recombined with the high-boiling component mixture after throttling in the high-temperature heat regenerator to participate in circulation.
Compared with the prior art, the invention has the following advantages and effects: the switching between the standby mode and the refrigeration mode can ensure that the refrigerant and the evaporator coil have larger heat exchange temperature difference, thereby ensuring that the evaporator obtains higher cooling speed. Meanwhile, due to the arrangement of the cold accumulator pipeline, the flow entering the evaporator is larger during switching, and the evaporator can obtain a higher cooling speed.
Drawings
FIG. 1 is a schematic structural diagram of a self-cascade refrigeration system for cryogenic water vapor capture provided by the present invention;
FIG. 2 is a graph of the temperature drop of a self-cascade refrigeration system for cryogenic water vapor capture according to the present invention operating in different modes.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
As shown in fig. 1, the self-cascade refrigeration system for trapping cryogenic water vapor provided by the invention comprises a compressor 1, an oil separator 2, a condenser 3, a rectification device 4, a high-temperature heat regenerator 6, a low-temperature heat regenerator 7, a cold accumulator 10 and an evaporator 11, wherein a kettle top heat exchanger 5 is arranged at the top of the rectification device 4;
all parts are connected by pipelines, and the connection relation of the high-pressure side is as follows: the exhaust port of the compressor 1 is connected with the inlet of the oil separator 2, the outlet of the oil separator 2 is connected with the inlet of the condenser 3, the outlet of the condenser 3 is connected with the inlet 4a of the rectifying device 4, the kettle bottom outlet 4b of the rectifying device 4 is connected with the inlet of the second throttle valve 12, the kettle top outlet 5a of the rectifying device 4 is connected with the high-pressure side inlet 6a of the high-temperature heat regenerator 6, the high-pressure side outlet 6b of the high-temperature heat regenerator 6 is connected with the high-pressure side inlet 7a of the low-temperature heat regenerator 7, and the high-pressure side outlet 7b of the low-temperature heat regenerator 7 is connected with the inlet of the first throttle valve 8. The connection relation of the low-voltage side is as follows: an air suction port of the compressor 1 is connected with an outlet 5c of a kettle top heat exchanger 5 of the rectifying device 4, an inlet 5b of the kettle top heat exchanger 5 is connected with a low-pressure side outlet 6d of the high-temperature heat regenerator 6, a low-pressure side inlet 6c of the high-temperature heat regenerator 6 is respectively connected with an outlet of the second throttle valve 12 and a low-pressure side outlet 7d of the low-temperature heat regenerator 7, a low-pressure side inlet 7c of the low-temperature heat regenerator 7 is connected with an outlet of the evaporator 11, and an inlet of the evaporator 11 is connected with the first throttle valve 8.
A first standby pipeline 91 and a cold storage pipeline 92 which are connected with the evaporator 11 in parallel are sequentially arranged below the first throttle valve 8; the first standby pipeline 91 is communicated with the refrigerant inlet pipeline and the refrigerant outlet pipeline, and a first electromagnetic valve 13 is distributed on the first standby pipeline 91; an upper inlet 10a and an upper outlet 10b of the regenerator 10 are communicated to a refrigerant inlet line and a refrigerant outlet line through a regenerator line 92, respectively, and a lower outlet 10c of the regenerator 10 is connected to an inlet of the evaporator 11; a second electromagnetic valve 14 is arranged on a connecting pipeline between an upper inlet 10a of the regenerator 10 and a refrigerant inlet pipeline, a third electromagnetic valve 15 is arranged on a connecting pipeline between an upper outlet 10b of the regenerator 10 and a refrigerant outlet pipeline, and a fifth electromagnetic valve 17 is arranged on a connecting pipeline between a lower outlet 10c of the regenerator 10 and an inlet of the evaporator 11; a fourth electromagnetic valve 16 is arranged on the refrigerant inlet pipeline;
a sixth electromagnetic valve 18 and a third throttle valve 19 are sequentially arranged between the outlet of the oil separator 2 and the inlet of the evaporator 11;
the first standby pipeline 91, the regenerator pipeline 92, the regenerator 10 and the evaporator 11 constitute a working space 9.
The control method of the self-cascade refrigeration system for trapping the cryogenic water vapor provided by the invention comprises the following steps:
the working process of the self-cascade refrigeration system for trapping the cryogenic water vapor is as follows:
the multi-element mixed working medium is compressed by a compressor 1 and then is changed into high-temperature and high-pressure gas, the high-temperature and high-pressure gas is condensed by an oil separator 2 and a condenser 3 and then enters a rectifying device 4, after heat and mass exchange, a high-boiling component mixture is condensed by the rectifying device 4 and separated from a low-boiling component mixture, the high-boiling component mixture flows out from an outlet at the bottom of the rectifying device 4, and the low-boiling component mixture participates in circulation from an outlet of a kettle top heat exchanger 5; the high-boiling component mixture enters the high-temperature heat regenerator 6 for evaporation and heat absorption after throttling expansion through the second throttling valve 12, and cold energy is provided for the low-boiling component mixture exchanging heat in the high-temperature heat regenerator 6; the evaporated high-boiling component mixture still has part of cold energy, flows through the kettle top heat exchanger 5 and precools the low-boiling component mixture therein, and further enhances the separation effect of the rectifying device 4 and the kettle top heat exchanger 5; the high-boiling component mixture enters the air suction port of the compressor 1 and participates in circulation again;
the low-boiling component mixture rises and flows out in the rectifying device 4, and after the low-boiling component mixture is pre-cooled by a rectifying action and a kettle top heat exchanger 5, the high-boiling component mixture mixed in the low-boiling component mixture is separated; after precooling the low-boiling component mixture by the kettle top heat exchanger 5 and the high-temperature heat regenerator 6, the low-boiling component mixture is further cooled by the evaporated low-boiling component mixture in the low-temperature heat regenerator 7, and the low-boiling component mixture serving as a low-temperature refrigerant enters a working space 9 (a dotted line frame part in fig. 1) after passing through a first throttle valve 8 so as to provide cold energy for the working space 9; the low-boiling component mixture after heat exchange flows out of the working space 9 and passes through the low-temperature heat regenerator 7 to be recombined with the high-boiling component mixture after throttling in the high-temperature heat regenerator 6 to participate in circulation.
In order to ensure the efficient operation of the system, three working modes of standby, refrigeration and defrosting are set, and the switching between the working modes is realized by the first solenoid valve 13 to the sixth solenoid valve 18 in the working space 9. When the temperature of the first throttle valve 8 reaches a low temperature, the standby mode is switched to the cooling mode, and the refrigerant (low-temperature refrigerant) originally flowing through the first standby pipeline 91 enters the evaporator 11, so that the coil of the evaporator 11 is cooled, and the use target is reached. Compared with a mode that a refrigerant of a common refrigeration system directly enters the evaporator 11 for coil cooling after being started (namely, the refrigerant directly enters the refrigeration mode after being started), the standby mode is switched to the refrigeration mode, so that the refrigerant and a coil of the evaporator 11 have larger heat exchange temperature difference, and the evaporator 11 obtains a higher cooling speed.
At the instant of switching between the two modes, the flow rate of the refrigerant does not change significantly. In order to further increase the cooling rate of the evaporator 11, a cold storage pipeline 92 is connected in parallel to the first standby pipeline 91, and part of the low-temperature refrigerant in the standby mode is stored therein, and when the system is switched to the cooling mode, the part of the refrigerant flows into the coil of the evaporator 11 along with the refrigerant in the pipeline, so that the flow rate of the refrigerant can be increased at the initial stage of the cooling mode, and the cooling rate is increased. Therefore, on the basis of the original rectification type self-cascade system, the cold accumulator 10 is added to accelerate the cooling speed of the evaporator during mode switching. Therefore, in summary, in the working space, the following working modes and switching can be performed:
(1) non-cold storage standby mode: the pre-cooling process of the refrigerating system and the recovery process of the unit are realized, and preparation is made for catching water vapor by the low-temperature coil pipe at any time. And opening the first electromagnetic valve 13, closing the second electromagnetic valve 14, the third electromagnetic valve 15, the fourth electromagnetic valve 16, the fifth electromagnetic valve 17 and the sixth electromagnetic valve 18, further throttling and cooling the low-temperature refrigerant by the first throttle valve 8, allowing the low-temperature refrigerant to flow through the first electromagnetic valve 13 and then enter the low-temperature heat regenerator 7, precooling the high-pressure refrigerant before throttling, and keeping the heat load at zero.
(2) Non-cold storage refrigeration mode: the low temperature coil is rapidly cooled to the desired lower temperature for moisture capture. In the standby mode, when the outlet of the first throttle valve 8 reaches a low temperature, the first electromagnetic valve 13 is closed, the fourth electromagnetic valve 16 is opened at the same time, the second electromagnetic valve 14, the third electromagnetic valve 15, the fifth electromagnetic valve 17 and the sixth electromagnetic valve 18 are kept closed, and the low-temperature refrigerant flows through the coil of the evaporator 11 to provide cold trap cooling capacity and then enters the low-temperature regenerator 7.
(3) Non-cold storage defrosting mode: in the non-cold storage refrigeration mode, the fourth electromagnetic valve 16 is closed, the sixth electromagnetic valve 18 is opened, the opening degree of the third throttle valve 19 is adjusted, part of the high-temperature compressor exhausts air and enters the coil of the evaporator 11, the temperature of the coil of the evaporator 11 is increased to be above 0 ℃, the defrosting process of the coil of the evaporator 11 is completed, the sixth electromagnetic valve 18 is closed again, and the fourth electromagnetic valve 16 is opened.
(4) Cold storage standby mode: and opening a second electromagnetic valve 14 and a third electromagnetic valve 15, closing a first electromagnetic valve 13, a fourth electromagnetic valve 16, a fifth electromagnetic valve 17 and a sixth electromagnetic valve 18, further throttling and cooling the low-temperature refrigerant by a first throttle valve 8, then enabling the low-temperature refrigerant to enter the cold accumulator 10, accumulating part of the refrigerant in the cold accumulator 10, enabling other refrigerants to flow out of an upper outlet 10b of the cold accumulator 10, enabling the other refrigerants to enter the low-temperature heat regenerator 7 after passing through the third electromagnetic valve 15.
(5) Cold storage refrigeration mode: in the cold accumulation standby mode, when the outlet of the first throttle valve 8 reaches low temperature, the third electromagnetic valve 15 is closed, the fourth electromagnetic valve 16 and the fifth electromagnetic valve 17 are opened, the first electromagnetic valve 13, the second electromagnetic valve 14, the third electromagnetic valve 15 and the sixth electromagnetic valve 18 are kept closed, and the low-temperature refrigerant accumulated in the cold accumulator 10 enters the coil of the evaporator 11 along with the incoming flow refrigerant in the refrigerant inlet pipeline to provide cold trap cooling capacity and then enters the low-temperature heat regenerator 7.
(6) Cold accumulation defrosting mode: in the cold storage refrigeration mode, the fourth electromagnetic valve 16 and the fifth electromagnetic valve 17 are closed, the sixth electromagnetic valve 18 is opened, the opening degree of the third throttle valve 19 is adjusted, part of the high-temperature compressor exhausts air and enters the coil of the evaporator 11, the temperature of the coil of the evaporator 11 is increased to be above 0 ℃, the defrosting process of the coil of the evaporator 11 is completed, the sixth electromagnetic valve 18 is closed again, and the fourth electromagnetic valve 16 and the fifth electromagnetic valve 17 are opened.
The experiment of the invention using the multicomponent mixed working medium composed of nitrogen and hydrocarbons can obtain the cooling curves in different modes as shown in figure 2 (the abscissa is time, and the ordinate is temperature). The temperature in fig. 2 is the outlet temperature of the working space 9 in fig. 1 (i.e. the temperature of the inlet 7c of the return low temperature regenerator 7). As can be seen from fig. 2, since the refrigerant in the cold accumulator 10 is to be cooled, the cold storage standby mode falls below-150 ℃ for a longer time than the non-cold storage standby mode; however, when the cooling mode is switched to the cooling mode, the time for the temperature to be reduced to minus 135 ℃ is reduced by adopting the cold accumulation cooling mode compared with the non-cold accumulation cooling mode, which shows that the arrangement of the cold accumulator 10 has a certain effect of improving the cooling rate of the evaporator coil after the cold accumulation standby mode is switched to the cold accumulation cooling mode.
The above-mentioned embodiments are intended to illustrate the technical solutions and advantages of the present invention, and it should be understood that the above-mentioned embodiments are only the most preferred embodiments of the present invention, and are not intended to limit the present invention, and any modifications, additions, equivalents, etc. made within the scope of the principles of the present invention should be included in the scope of the present invention.

Claims (6)

1. A self-cascade refrigeration system for trapping cryogenic water vapor is characterized by comprising a compressor, an oil separator, a condenser, a rectifying device, a high-temperature heat regenerator, a low-temperature heat regenerator, a cold accumulator and an evaporator which are connected through pipelines, wherein a kettle top heat exchanger is arranged at the top of the rectifying device;
the exhaust port of the compressor is connected with the inlet of the oil separator;
the inlet of the condenser is connected with the outlet of the oil separator, and the outlet of the condenser is connected with the inlet of the rectifying device;
the kettle bottom outlet of the rectifying device is connected with the low-pressure side inlet of the high-temperature heat regenerator through a second throttle valve; the kettle top outlet of the rectifying device is connected with the high-pressure side inlet of the high-temperature heat regenerator; the outlet of the kettle top heat exchanger is connected with the air suction port of the compressor; the inlet of the kettle top heat exchanger is connected with the outlet of the low-pressure side of the high-temperature heat regenerator;
the high-pressure side outlet of the high-temperature regenerator is connected with the high-pressure side inlet of the low-temperature regenerator; the low-pressure side inlet of the high-temperature heat regenerator is connected with the low-pressure side outlet of the low-temperature heat regenerator;
the high-pressure side outlet of the low-temperature heat regenerator is connected with the inlet of the evaporator through a first throttling valve, and the connecting pipeline is a refrigerant inlet pipeline; the low-pressure side inlet of the low-temperature heat regenerator is connected with the outlet of the evaporator, and the connecting pipeline is a refrigerant outlet pipeline;
a first standby pipeline and a cold accumulator pipeline which are connected with the evaporator in parallel are sequentially arranged below the first throttle valve; the first standby pipeline is communicated with the refrigerant inlet pipeline and the refrigerant outlet pipeline, and a first electromagnetic valve is arranged on the first standby pipeline; an upper inlet and an upper outlet of the regenerator are respectively communicated to a refrigerant inlet pipeline and a refrigerant outlet pipeline through a regenerator pipeline, and a lower outlet of the regenerator is connected with an inlet of the evaporator; a second electromagnetic valve is arranged on a connecting pipeline between an upper inlet of the regenerator and a refrigerant inlet pipeline, a third electromagnetic valve is arranged on a connecting pipeline between an upper outlet of the regenerator and a refrigerant outlet pipeline, and a fifth electromagnetic valve is arranged on a connecting pipeline between a lower outlet of the regenerator and an inlet of the evaporator; a fourth electromagnetic valve is arranged on the refrigerant inlet pipeline;
a sixth electromagnetic valve and a third throttle valve are sequentially arranged between the outlet of the oil separator and the inlet of the evaporator;
the first standby pipeline, the cold accumulator and the evaporator form a working space.
2. The self-cascade refrigeration system for cryogenic water vapor capture of claim 1, wherein the first, second, third, fourth, fifth, and sixth solenoid valves are on-off solenoid valves.
3. The self-cascade refrigeration system for cryogenic water vapor capture according to claim 1, wherein the self-cascade refrigeration system employs a multi-component mixed working fluid selected from nitrogen, argon, alkane, alkene or halogenated hydrocarbon.
4. The self-cascade refrigeration system for cryogenic water vapor capture of claim 1 comprising the operating modes of: the cold storage defrosting control system comprises a non-cold storage standby mode, a non-cold storage refrigerating mode, a non-cold storage defrosting mode and a cold storage defrosting mode, wherein the working modes are switched by a first electromagnetic valve and/or a second electromagnetic valve and/or a third electromagnetic valve and/or a fourth electromagnetic valve and/or a fifth electromagnetic valve and/or a sixth electromagnetic valve.
5. A method of controlling a self-cascade refrigeration system for cryogenic water vapor capture as claimed in any one of claims 1 to 4, the method comprising:
non-cold storage standby mode: opening a first electromagnetic valve, closing a second electromagnetic valve, a third electromagnetic valve, a fourth electromagnetic valve, a fifth electromagnetic valve and a sixth electromagnetic valve, further throttling and cooling the low-temperature refrigerant by a first throttling valve, and enabling the low-temperature refrigerant to flow through the first electromagnetic valve and then enter a low-temperature heat regenerator;
non-cold storage refrigeration mode: in a non-cold storage standby mode, when the outlet of the first throttle valve reaches low temperature, the first electromagnetic valve is closed, the fourth electromagnetic valve is opened at the same time, the first electromagnetic valve, the second electromagnetic valve, the third electromagnetic valve, the fifth electromagnetic valve and the sixth electromagnetic valve are kept closed, and a low-temperature refrigerant flows through a coil pipe of the evaporator to provide cold energy of a cold trap and then enters a low-temperature heat regenerator;
non-cold storage defrosting mode: in a non-cold storage refrigeration mode, closing the fourth electromagnetic valve, opening the sixth electromagnetic valve, adjusting the opening degree of the third throttle valve, exhausting gas from a part of high-temperature compressor, entering a coil of the evaporator, raising the temperature of the evaporator coil to be above 0 ℃, completing the defrosting process of the evaporator coil, re-closing the sixth electromagnetic valve, and opening the fourth electromagnetic valve;
cold storage standby mode: opening a second electromagnetic valve and a third electromagnetic valve, closing the first electromagnetic valve, a fourth electromagnetic valve, a fifth electromagnetic valve and a sixth electromagnetic valve, further throttling and cooling the low-temperature refrigerant by a first throttle valve, allowing the low-temperature refrigerant to flow through the second electromagnetic valve to enter a regenerator, allowing part of the low-temperature refrigerant to accumulate in the regenerator, and allowing the other part of the refrigerant to flow through the third electromagnetic valve from an upper outlet of the regenerator to enter a low-temperature regenerator;
cold storage refrigeration mode: when the outlet of the first throttle valve reaches low temperature, the third electromagnetic valve is closed, the fourth electromagnetic valve and the fifth electromagnetic valve are opened, the first electromagnetic valve, the second electromagnetic valve, the third electromagnetic valve and the sixth electromagnetic valve are kept closed, and the low-temperature refrigerant accumulated in the cold accumulator enters a coil pipe of the evaporator along with the low-temperature refrigerant in the refrigerant inlet pipeline to provide cold energy of a cold trap and then enters a low-temperature heat regenerator;
cold accumulation defrosting mode: and in the cold storage refrigeration mode, closing the fourth electromagnetic valve and the fifth electromagnetic valve, opening the sixth electromagnetic valve, adjusting the opening degree of the third throttle valve, exhausting air from a part of the high-temperature compressor, entering a coil of the evaporator, raising the temperature of the coil of the evaporator to be above 0 ℃, completing the defrosting process of the coil of the evaporator, re-closing the sixth electromagnetic valve, and opening the fourth electromagnetic valve and the fifth electromagnetic valve.
6. The control method of the self-cascade refrigeration system for cryogenic water vapor capture according to claim 5, characterized in that the multi-component mixed working medium is compressed by a compressor and then is changed into high-temperature and high-pressure gas, the gas is condensed by an oil separator and a condenser and then enters a rectifying device, after heat and mass exchange, a high-boiling component mixture is condensed and separated from a low-boiling component mixture in the rectifying device and flows out from a bottom outlet of the rectifying device, and the low-boiling component mixture participates in circulation from an outlet of a kettle top heat exchanger; the high-boiling component mixture enters a high-temperature heat regenerator for evaporation and heat absorption after being throttled and expanded by a second throttle valve, and cold energy is provided for the low-boiling component mixture subjected to heat exchange in the high-temperature heat regenerator; the evaporated high-boiling component mixture still has part of cold energy, flows through the kettle top heat exchanger and precools the low-boiling component mixture in the kettle top heat exchanger, and further enhances the separation effect of the rectifying device; the high-boiling component mixture enters an air suction port of the compressor and participates in circulation again;
the low-boiling component mixture rises and flows out in the rectifying device, and after the low-boiling component mixture is subjected to rectification and precooling by a kettle top heat exchanger, the high-boiling component mixture mixed in the low-boiling component mixture is separated; after precooling the low-boiling component mixture by the kettle top heat exchanger and the high-temperature heat regenerator, further cooling the low-boiling component mixture in the low-temperature heat regenerator by the evaporated low-boiling component mixture, and enabling the low-boiling component mixture to enter a working space as a low-temperature refrigerant after passing through a first throttling valve so as to provide cold energy for the working space; the low-boiling component mixture after heat exchange flows out of the working space and passes through the low-temperature heat regenerator, and then is recombined with the high-boiling component mixture after throttling in the high-temperature heat regenerator to participate in circulation.
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