CN108709333B - Operation method and system of secondary throttling middle complete cooling refrigerating system - Google Patents

Operation method and system of secondary throttling middle complete cooling refrigerating system Download PDF

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CN108709333B
CN108709333B CN201810800290.6A CN201810800290A CN108709333B CN 108709333 B CN108709333 B CN 108709333B CN 201810800290 A CN201810800290 A CN 201810800290A CN 108709333 B CN108709333 B CN 108709333B
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pressure stage
pressure
interface
temperature evaporator
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CN108709333A (en
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杨永安
李瑞申
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Tianjin University of Commerce
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Tianjin University of Commerce
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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
    • F25B13/00—Compression machines, plants or systems, with reversible cycle
    • 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
    • F25B41/40—Fluid line arrangements
    • 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
    • F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
    • F25B47/02—Defrosting cycles
    • 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

Abstract

The invention discloses an operation method and system of a secondary throttling middle complete cooling refrigerating system, and aims to provide a method and system for defrosting a low-temperature evaporator gear by adopting a low-pressure-stage compressor heat pump cycle. In each low-pressure stage unit, there are a medium-temperature evaporator for realizing medium-temperature refrigeration and a low-temperature evaporator for realizing low-temperature refrigeration or defrosting, the method is as follows: when the low-temperature evaporator needs to defrost, the low-pressure level compressor realizing the defrosting function is converted into a high-pressure level compressor to operate through valve switching, the low-temperature compressor in the low-pressure level unit realizing the defrosting function absorbs working media from the low-pressure level compressor realizing the refrigerating function, the low-temperature evaporator to be defrosted is condensed and heated after compression, the defrosting is realized, and when a plurality of low-temperature evaporators need to defrost, the defrosting is realized in a gear mode. The invention has the advantages of two-stage compression cycle in defrosting cycle and refrigeration cycle, small temperature fluctuation of the refrigeration house, simple structure and high efficiency.

Description

Operation method and system of secondary throttling middle complete cooling refrigerating system
Technical Field
The invention relates to the technical field of refrigeration, in particular to an operation method of a secondary throttling and intermediate complete cooling two-stage compression refrigeration system with a medium-temperature evaporator by adopting a heat pump for defrosting and a refrigeration system.
Background
In the freezer, when the heat exchanger cooling surface is covered by the frost layer, if not in time clear away, the frost accumulation will make the compressor inhale the temperature reduction, and exhaust temperature rises to the air passage is stopped up, reduces heat transfer area, and the flow resistance of air is showing and is increasing, and heat exchange efficiency is violently reduced, and refrigerating plant running performance declines. The defrosting effect is also key to fully play the equipment capacity of the refrigeration house, reduce overhaul cost, save electricity and ensure the food quality.
The existing defrosting method of the evaporator in the refrigeration house mainly comprises the following steps: an electric heating method, a water spraying method, a reverse circulation defrosting method and the like. The defrosting methods of the electric heating method and the water spraying method are both external heating frost layers, and frost is melted from outside to inside, so that the heat quantity of defrosting is much larger than a theoretical value in practice, the defrosting method consumes more energy, has higher operation cost, and is seldom used from the aspects of safety, stability and energy conservation. The heat of the reverse circulation defrosting method is derived from the power consumption of an outdoor environment and a compressor, the flow direction of working media of the whole refrigerating system is temporarily changed by changing the connection mode of the four-way reversing valve, and then the heat transfer direction is changed, so that the evaporator is changed into a condenser, and the defrosting effect is achieved by heating the evaporator, but at the moment, the refrigerating cycle is stopped during defrosting, and all evaporators cannot continuously refrigerate. The reverse circulation defrosting method has high defrosting efficiency and is energy-saving and reliable. However, the defrosting method is only suitable for a single-stage compression refrigerating system with a simple structure, and for a double-stage compression refrigerating system with a low evaporation temperature, when the reverse circulation is adopted to defrost the evaporator, if the whole refrigerating system reversely operates, all evaporators of the refrigerator are switched to be condensers, and the temperature difference between the surface temperature of the evaporator and the temperature in the refrigerator is large, the defrosting time is long, the temperature fluctuation of the refrigerator is large, the food consumption is caused, and the economic loss is caused. Therefore, in order for a dual stage compression system to remain efficient, the evaporator must be defrosted in an orderly and efficient manner.
At present, a method for effectively defrosting in a two-stage compression refrigeration system comprises a single-stage compression heat pump circulation method, namely a pipeline connected with an inlet and an outlet of an evaporator is divided into a refrigeration branch and a defrosting branch on the original two-stage compression refrigeration system, an inlet defrosting pipeline of the evaporator is connected with an exhaust end of a high-pressure stage compressor or a low-pressure stage compressor, and an outlet of the evaporator is connected with a gas-liquid separator with larger volume. When the evaporator needs to refrigerate, the refrigerating branch is connected with the evaporator by switching the valve, and the evaporator refrigerates. When the evaporator needs to defrost, the defrosting branch is connected with the evaporator by switching the valve to defrost the evaporator. The single-stage compression heat pump cycle is operated in the defrosting method, when the double-stage compression refrigeration cycle is converted into the single-stage compression heat pump defrosting cycle, the pressure difference of the operation of the compressors participating in the single-stage compression heat pump cycle defrosting is increased sharply, the impact on the compressors can be caused, the compressors are damaged, the temperature of working media entering the evaporator for defrosting in the single-stage compression heat pump defrosting cycle is low, the defrosting speed is low, the time for diffusing heat around the evaporator is long, and the defrosting efficiency is reduced; in addition, when defrosting the evaporator, a large amount of liquid working media condensed by the evaporator flow into the gas-liquid separator, and the liquid working media are accumulated for a long time, so that the liquid working media are easily sucked by the low-pressure-stage compressor to form wet compression of the compressor, and the compressor is damaged to form economic loss.
In addition, the existing refrigeration house can only realize single refrigeration temperature generally, and provides refrigeration capacity between refrigeration or freezing according to use needs, so that the refrigeration house is inconvenient to use.
Disclosure of Invention
The invention aims at solving the technical defects in the prior art, and provides an operation method of a secondary throttling middle complete cooling refrigerating system, which has high defrosting efficiency and small temperature fluctuation and is beneficial to long-term stable operation of a compressor.
The invention further aims to provide a double-stage compression refrigerating system which adopts a heat pump cycle to defrost a low-temperature evaporator gear, has small temperature fluctuation and stable operation, and can provide secondary throttling and intermediate complete cooling of cold energy between a refrigerating room and a freezing room.
The technical scheme adopted for realizing the purpose of the invention is as follows:
a method of operating a secondary throttling intercooling refrigeration system having a low temperature evaporator and a medium temperature evaporator disposed in each low pressure stage unit, the medium temperature evaporator being for performing medium temperature refrigeration and the low temperature evaporator being for performing low temperature refrigeration or defrost, the method comprising the steps of: when all low-pressure units realize the refrigeration function, the medium-temperature evaporator evaporates medium-pressure saturated liquid working medium into medium-pressure saturated vapor to realize medium-temperature refrigeration; the low-temperature evaporator evaporates the low-pressure liquid working medium into low-pressure vapor to realize low-temperature refrigeration; when the low-temperature evaporator needs defrosting, the low-pressure stage compressor realizing the defrosting function is converted into a high-pressure stage compressor to operate through valve switching, the low-pressure stage compressor in the low-pressure stage unit realizing the defrosting function absorbs medium-pressure superheated steam from the low-pressure stage compressor realizing the refrigerating function or medium-pressure saturated steam from the intercooler, and the medium-pressure superheated steam is compressed and then sent into the low-temperature evaporator to be defrosted, so that the low-temperature evaporator is condensed and heated, defrosting is realized, and the low-temperature evaporator in the low-pressure stage unit realizing the refrigerating function still realizes the refrigerating function; after defrosting is finished, the low-pressure stage unit for realizing the defrosting function is switched by a valve to realize the refrigerating function; when a plurality of low-temperature evaporators need defrosting, the defrosting is realized in a gear mode.
A refrigerating system for realizing the operation method adopts a secondary throttling and intermediate complete cooling of heat pump defrosting, which comprises a high-pressure stage compressor set, a condenser, a first throttling valve, an intermediate cooler and a plurality of groups of low-pressure stage units; each low-pressure stage unit comprises a low-pressure stage compressor, a first four-way reversing valve, a second throttling valve, a low-temperature evaporator, a middle-temperature evaporator, a first one-way valve and a second one-way valve, wherein the air suction end of the low-pressure stage compressor is connected with the fourth interface of the first four-way reversing valve, the air discharge end of the low-pressure stage compressor is connected with the second interface of the first four-way reversing valve, the third interface of the first four-way reversing valve is respectively connected with the inlet of the first one-way valve and the outlet of the second one-way valve, the first interface of the first four-way reversing valve is connected with the first interface of the second throttling valve through the low-temperature evaporator, the second interface of the second throttling valve is connected with the second interface of the middle-temperature evaporator in parallel and is connected with the liquid outlet of the middle-temperature evaporator, the first interface of the middle-temperature evaporator is connected with the first interface of the middle-temperature evaporator in parallel and is connected with the first air inlet of the middle-temperature evaporator, the first interface of the first four-way reversing valve is connected with the first air inlet of the middle-temperature evaporator in parallel and the air inlet of the middle-temperature evaporator, the first air inlet of the middle-temperature evaporator is connected with the first air inlet of the middle-temperature evaporator in parallel and the middle-pressure stage unit is connected with the air inlet of the middle-pressure stage unit in parallel and the high-pressure stage is respectively; and the exhaust end of the high-pressure stage compressor unit is connected with the liquid inlet of the intercooler through the condenser and the first throttle valve.
When a plurality of high-pressure compressors are adopted, the air suction interface of each high-pressure compressor is connected in parallel to serve as the air suction end of the high-pressure compressor unit, and the air discharge interface of each high-pressure compressor is connected in parallel to serve as the air discharge end of the high-pressure compressor unit.
The number of low-pressure stage units is at least three.
A refrigerating system for realizing secondary throttling and intermediate complete cooling of the operation method comprises a high-pressure stage compressor unit, a condenser, a first throttle valve, an intermediate cooler and a plurality of groups of low-pressure stage units; each low-pressure stage unit comprises a low-pressure stage compressor, a first four-way reversing valve, a second throttle valve, a low-temperature evaporator, a middle-temperature evaporator, a first one-way valve and a second one-way valve, wherein the air suction end of the low-pressure stage compressor is connected with the fourth interface of the first four-way reversing valve, the air discharge end of the low-pressure stage compressor is connected with the second interface of the first four-way reversing valve, the third interface of the first four-way reversing valve is respectively connected with the inlet of the first one-way valve and the outlet of the second one-way valve, the first interface of the first four-way reversing valve is connected with the first interface of the second throttle valve through the low-temperature evaporator, the second interface of the second throttle valve is connected with the second interface of the second four-way reversing valve, the second interface of the middle-temperature evaporator is connected with the third interface of the second four-way reversing valve, and in a plurality of groups of low-pressure stage units, the first interface of the middle-temperature evaporator is connected with the fourth interface of the fourth four-way reversing valve in parallel and is connected with the fourth interface of the middle cooler in parallel; the outlet of the first one-way valve is connected in parallel and connected with the second air inlet of the intercooler, and the inlet of the second one-way valve is connected in parallel and connected with the air suction end of the high-pressure stage compressor unit and the air outlet of the intercooler respectively; and the exhaust end of the high-pressure stage compressor unit is connected with the liquid inlet of the intercooler through the condenser and the first throttle valve.
A refrigerating system for realizing the secondary throttling and intermediate complete cooling of the operation method comprises a high-pressure stage compressor unit, a condenser, a first throttling valve, an intercooler, a third four-way reversing valve and a plurality of low-pressure stage units; each low-pressure stage unit comprises a low-pressure stage compressor, a first four-way reversing valve, a second throttle valve, a low-temperature evaporator, a medium-temperature evaporator, a first one-way valve and a second one-way valve, wherein the air suction end of the low-pressure stage compressor is connected with a fourth interface of the first four-way reversing valve, the air discharge end of the low-pressure stage compressor is connected with a second interface of the first four-way reversing valve, a third interface of the first four-way reversing valve is connected with an inlet of the first one-way valve and an outlet of the second one-way valve respectively, and the first interface of the first four-way reversing valve is connected with the first interface of the second throttle valve through the low-temperature evaporator; in the low-pressure stage units, a first interface of the intermediate-temperature evaporator is connected in parallel and connected with a first air inlet of the intercooler, a second interface of the second throttle valve is connected in parallel with a second interface of the intermediate-temperature evaporator and connected with a liquid outlet of the intercooler, an outlet of the first one-way valve is connected in parallel and connected with a second interface of the third four-way reversing valve, an inlet of the second one-way valve is connected in parallel and connected with an air suction end of the high-pressure stage compressor unit and a third interface of the third four-way reversing valve respectively, the first interface of the third four-way reversing valve is connected with a second air inlet of the intercooler, and a fourth interface of the third four-way reversing valve is connected with an air outlet of the intercooler; and the exhaust end of the high-pressure stage compressor unit is connected with the liquid inlet of the intercooler through the condenser and the first throttle valve.
The refrigerating system for realizing the secondary throttling middle complete cooling of the operation method comprises a high-pressure stage compressor unit, a condenser, a first throttle valve, a third four-way reversing valve, an intercooler and a plurality of low-pressure stage units; each low-pressure stage unit comprises a low-pressure stage compressor, a first four-way reversing valve, a second throttle valve, a low-temperature evaporator, a medium-temperature evaporator, a first one-way valve and a second one-way valve, wherein the air suction end of the low-pressure stage compressor is connected with a fourth interface of the first four-way reversing valve, the air discharge end of the low-pressure stage compressor is connected with a second interface of the first four-way reversing valve, a third interface of the first four-way reversing valve is connected with an inlet of the first one-way valve and an outlet of the second one-way valve respectively, the first interface of the first four-way reversing valve is connected with the first interface of the second throttle valve through the low-temperature evaporator, and the second interface of the second throttle valve is connected with the second interface of the second four-way reversing valve; the first interface of the intermediate temperature evaporator is connected in parallel and connected with the first air inlet of the intercooler, the other end of the intermediate temperature evaporator is connected with the third interface of the second four-way reversing valve, and the first interface and the fourth interface of the second four-way reversing valve are connected in parallel and connected with the liquid outlet of the intercooler; the outlet of the first one-way valve is connected in parallel and connected with the second interface of the third four-way reversing valve, the inlet of the second one-way valve is connected in parallel and connected with the suction end of the high-pressure stage compressor unit and the third interface of the third four-way reversing valve respectively, the first interface of the third four-way reversing valve is connected with the second air inlet of the intercooler, and the fourth interface of the third four-way reversing valve is connected with the air outlet of the intercooler; and the exhaust end of the high-pressure stage compressor unit is connected with the liquid inlet of the intercooler through the condenser and the first throttle valve.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the operation method of the refrigeration system, the switching of the refrigeration and defrosting modes of the low-pressure stage unit is realized through the switching of the valve. In the defrosting mode, the low-pressure stage compressor realizing the defrosting function is converted into a high-pressure stage compressor to operate, the low-temperature compressor in the low-pressure stage unit realizing the defrosting function absorbs medium-pressure superheated steam from the low-pressure stage compressor realizing the refrigerating function or medium-pressure saturated steam from the intercooler, reverse circulation defrosting of the low-pressure stage unit is realized after compression, circulation during defrosting and circulation during refrigerating are two-stage compression circulation, and therefore a dynamic system is formed, temperature fluctuation is small, defrosting efficiency is high, and energy is saved. Meanwhile, the compressor can stably operate, and the service life of the system is prolonged.
2. The invention adopts the secondary throttling middle-complete cooling refrigerating system with the medium-temperature evaporator for defrosting by the heat pump, when the medium-low temperature evaporator in the low-pressure stage unit is defrosted, the switching of the refrigerating mode and the defrosting mode of the low-pressure stage unit is realized by switching the valve, the low-pressure stage compressor with the defrosting function is switched into the high-pressure stage compressor to operate in the defrosting mode, and the defrosting cycle and the refrigerating cycle are two-stage compression cycles, thereby forming a dynamic refrigerating system, being more flexible and convenient to use, having high defrosting efficiency and saving energy.
3. The low-pressure stage compressor in the low-pressure stage unit for defrosting the refrigerating system can absorb the medium-pressure superheated steam which is not cooled by the intercooler, the medium-pressure superheated steam absorbs the compressed and discharged hot gas with higher temperature by the low-pressure compressor of the low-pressure stage unit for defrosting, and the temperature of the working medium entering the low-temperature evaporator of the low-pressure stage unit for defrosting is higher, so that the defrosting effect is better, and the defrosting speed is higher. When the low-temperature evaporators in all the low-pressure stage units do not need defrosting, the high-pressure stage compressor sucks the medium-pressure saturated steam cooled by the intercooler through valve switching, the medium-pressure saturated steam is sucked and compressed by the high-pressure stage compressor to discharge hot gas, the temperature is low, the condensation effect is good, and the refrigeration efficiency is high.
4. In the refrigerating system, when the evaporator in the low-pressure stage unit is defrosted, the low-pressure stage compressor is converted into the high-pressure stage compressor to operate, the defrosting cycle of the low-pressure stage unit works between medium pressure and high pressure, when the low-pressure stage unit is converted from the refrigerating cycle into the defrosting cycle, the pressure difference change of the work between the air suction and the air discharge of the compressor in the low-pressure stage unit is smaller, the heat dissipation of the compressor is better, and the compressor is protected.
5. The invention adopts the secondary throttling middle complete cooling refrigerating system with the medium-temperature evaporator for heat pump defrosting, the heat quantity for defrosting the evaporator in the low-pressure stage unit is derived from the input work of the evaporator and the compressor in the refrigeration low-pressure stage unit, the heat quantity supply during defrosting is sufficient and not limited, the full defrosting can be realized, the defrosting efficiency is higher, and the invention is more suitable for a large-scale double-stage compression refrigerating system.
6. In the refrigeration system, the low-pressure-stage compressor heat pump cycle is adopted to defrost the low-temperature evaporator wheel gear, and meanwhile, in the defrosting process, the low-pressure-stage compressors are sequentially converted into the high-pressure-stage compressors to operate, so that the lubricating oil of the high-pressure-stage compressors and the low-pressure-stage compressors is convenient to return oil uniformly, the wear degree of the high-pressure-stage compressors and the low-pressure-stage compressors is uniform, and the wear degree of the high-pressure-stage compressors and the low-pressure-stage compressors is uniform. The system is simple and the efficiency is high. Compared with a refrigerating system with a defrosting evaporator and a defrosting branch, the refrigerating system is simpler in structure and reduces the initial investment of the system.
7. The invention adopts a reverse circulation heat pump defrosting method to defrost the low-temperature evaporator in the secondary throttling middle complete cooling refrigerating system with the medium-temperature evaporator by using the heat pump defrosting, and heats the frost from the inside of the frost layer, so that the frost is easy to fall off from the cooling surface, and the heat quantity of the defrosting is much smaller than a theoretical value in practice. Meanwhile, the frost layer melts from inside to outside, and no water vapor escapes to the outside of the evaporator in the initial stage of defrosting. Only after the frost is melted and shed, the heat on the ribbed tube radiates outwards, but the defrosting stage tends to end at the moment, so that the heat exchange amount with the internal and surrounding enclosing structures of the warehouse is small, and the defrosting efficiency is higher.
8. The invention adopts the heat pump to defrost the secondary throttling middle complete cooling refrigerating system with the medium temperature evaporator, the number of the high-pressure stage compressors is not limited, the number of the low-pressure stage units is more than three, and the variable flow circulation of the high-pressure stage and the low-pressure stage can be realized according to different working condition requirements and different cold energy requirements, so that the optimal capacity ratio between the high-pressure stage and the low-pressure stage is matched.
9. The secondary throttling middle complete cooling refrigerating system with the medium-temperature evaporator for defrosting by adopting the heat pump can simultaneously prepare the refrigerating capacity at two evaporating temperatures, and is particularly suitable for being applied to a refrigeration house system to simultaneously provide the refrigerating capacity between refrigeration houses and freezing houses.
10. The invention adopts the secondary throttling middle-complete cooling refrigeration system with the middle-temperature evaporator for defrosting by adopting high-temperature hot gas, and when the low-temperature evaporator in the low-pressure stage unit is defrosted, the heat source for defrosting the low-temperature evaporator in the defrosting low-pressure stage unit is the middle-pressure superheated gas. The low-pressure stage compressor in the defrosting low-pressure stage unit directly sucks medium-pressure steam with higher superheat degree from the exhaust end of the low-pressure stage compressor in the refrigerating low-pressure stage unit, the high-pressure working medium discharged by the low-pressure stage compressor in the defrosting low-pressure stage unit has higher temperature, the working medium entering the low-temperature evaporator in the defrosting low-pressure stage unit has higher temperature, better defrosting effect and higher defrosting speed.
Drawings
FIG. 1 is a schematic diagram of a hot gas defrost, non-flooded secondary throttling intercooling refrigeration system of embodiment 1 of the invention;
FIG. 2 is a schematic diagram showing the structure of a hot gas defrost flooded secondary throttling intercooling refrigeration system of embodiment 2 of the invention;
FIG. 3 is a schematic diagram showing the construction of a non-flooded secondary throttling intermediate full cooling refrigeration system for hot air defrost in accordance with embodiment 3 of the present invention;
FIG. 4 is a schematic diagram showing the structure of a full-liquid type secondary throttling intermediate full-cooling refrigeration system for hot air defrosting in accordance with embodiment 4 of the present invention;
fig. 5 shows a schematic diagram of an intercooler interface.
Detailed Description
The invention will be described in detail below with reference to the drawings and the specific embodiments.
The design key points of the invention are as follows: when defrosting, the low-pressure stage compressor is changed into a high-pressure stage compressor through valve switching, and the original high-pressure stage compressor can be stopped partially or completely, so that the medium-pressure superheated steam from the low-pressure stage compressor for realizing the refrigeration function or the medium-pressure saturated steam from the intercooler is sucked by the low-pressure stage compressor for defrosting, and enters the low-temperature evaporator to be defrosted after being compressed, and the defrosted evaporator is converted into a two-stage compression condenser. And (5) defrosting one by one (or in groups), and refrigerating each evaporator through valve switching after defrosting. The specific technical scheme is as follows:
the invention relates to an operation method of a secondary throttling middle complete cooling refrigerating system, which is characterized in that a middle temperature evaporator and a low temperature evaporator are arranged in each low-pressure stage unit, the middle temperature evaporator is used for realizing middle temperature refrigeration, the low temperature evaporator is used for realizing low temperature refrigeration or defrosting, and the operation method comprises the following steps: when all low-pressure units realize the refrigeration function, the medium-temperature evaporator evaporates medium-pressure saturated liquid working medium into medium-pressure saturated vapor to realize medium-temperature refrigeration; the low-temperature evaporator evaporates the low-pressure liquid working medium into low-pressure vapor to realize low-temperature refrigeration; when the low-temperature evaporator needs to defrost, the low-pressure stage compressor realizing the defrosting function is converted into a high-pressure stage compressor to operate through valve switching, the low-pressure stage compressor in the low-pressure stage unit realizing the defrosting function absorbs medium-pressure superheated steam from the low-pressure stage compressor realizing the refrigerating function or medium-pressure saturated steam from the intercooler, and the medium-pressure superheated steam is compressed and then sent into the low-temperature evaporator to be defrosted, so that the low-temperature evaporator is condensed and heated, the defrosting is realized, and the low-temperature evaporator in the low-pressure stage unit realizing the refrigerating function still realizes the refrigerating function; after defrosting is finished, the low-pressure stage unit for realizing the defrosting function is switched by a valve to realize the refrigerating function. When a plurality of low-temperature evaporators need defrosting, the defrosting is realized in a gear mode.
In the invention, the number of the high-pressure stage compressors in the high-pressure stage compressor unit is one or more, and the number of the low-pressure stage units is at least three. When the number of the high-pressure stage compressors is 1 and the number of the low-pressure stage units is three, the high-pressure stage compressors are required to be stopped for realizing reverse circulation defrosting. The drawing shows that the high-pressure stage compressor unit comprises 2 high-pressure stage compressors, the number of low-pressure stage units is 4, and if one low-pressure stage unit is defrosted and the two high-pressure stage compressors are completely stopped, the operation ratio of the high-pressure stage to the low-pressure stage is 1:3, if one high-pressure stage compressor operates and the other one is stopped when one low-pressure stage unit is defrosted, the operation ratio of the high-pressure stage to the low-pressure stage is 2:3. if 3 high-pressure compressors are arranged in the high-pressure compressor unit, 6 low-pressure units are arranged, and the operation proportion types of the high-pressure compressor and the low-pressure compressor are more when defrosting. In the defrosting process, whether the high-pressure stage compressor is stopped or partially stopped is determined according to the ratio of the high-pressure stage to the low-pressure stage machine head, the specific working condition, the defrosting quality and the like.
In the secondary throttling middle-complete cooling refrigerating system with the medium-temperature evaporator for defrosting by adopting the heat pump, when the medium-low temperature evaporator in the low-pressure stage unit is defrosted, the system is divided into a full liquid supply type and a non-full liquid supply type according to the state of medium pressure working media in the front of the second throttling valve of the refrigerating low-pressure stage unit and the medium-temperature evaporator. The working medium entering the low-temperature evaporator and the medium-temperature evaporator in the full-liquid supply type system has low dryness, high heat exchange efficiency and small heat exchanger area required by the low-temperature evaporator and the medium-temperature evaporator. The system for supplying liquid without filling liquid has simple structure, less parts and lower cost. Meanwhile, in the refrigeration system, the corresponding low-pressure stage compressor can suck medium-pressure saturated vapor from the intercooler during defrosting, and can also suck vapor with higher medium-pressure superheat degree which is not cooled by the intercooler. In examples 1 and 2, the low-temperature compressor in the low-pressure stage unit that realizes the defrosting function absorbs the medium-pressure saturated vapor from the intercooler and compresses the same, and in examples 3 and 4, the low-temperature compressor in the low-pressure stage unit that realizes the defrosting function absorbs the vapor with a higher medium-pressure superheat degree from the low-pressure stage compressor that realizes the refrigerating function and compresses the same, and then defrost the same. The medium-pressure superheated steam is sucked into the high-temperature hot gas discharged by compression through the low-pressure compressor of the defrosting low-pressure stage unit, and the temperature of working medium entering the low-temperature evaporator of the defrosting low-pressure stage unit is higher, so that the defrosting effect is better, and the defrosting speed is higher.
The method of the invention can be realized by the following refrigeration systems:
example 1
The structural schematic diagram of the full-liquid type secondary throttling intermediate complete cooling refrigerating system for hot gas defrosting is shown in fig. 1, and comprises a high-pressure stage compressor unit, a condenser 5, a first throttling valve 4-1, an intercooler 3 and a plurality of groups of low-pressure stage units. In this embodiment, the high-pressure stage compressor unit includes one or more high-pressure stage compressors 1-2, and when a plurality of high-pressure stage compressors 1-2 are adopted, the air suction interface of each high-pressure stage compressor 1-2 is connected in parallel to serve as the air suction end of the high-pressure stage compressor unit, and the air discharge interface of each high-pressure stage compressor 1-2 is connected in parallel to serve as the air discharge end of the high-pressure stage compressor unit. The low-pressure stage units can be used for refrigeration cycle or defrosting cycle, each low-pressure stage unit comprises a low-pressure stage compressor 1-1, a first four-way reversing valve 2-1, a second throttle valve 4-2, a low-temperature evaporator 6-1, a medium-temperature evaporator 6-2, a first one-way valve 7-1 and a second one-way valve 7-2, the air suction end of the low-pressure stage compressor 1-1 is connected with a fourth interface of the first four-way reversing valve 2-1, the air discharge end of the low-pressure stage compressor 1-1 is connected with a second interface of the first four-way reversing valve 2-1, a third interface of the first four-way reversing valve 2-1 is respectively connected with an inlet of the first one-way valve 7-1 and an outlet of the second one-way valve 7-2, the first port of the first four-way reversing valve 2-1 is connected with the first port of the second throttle valve through the low-temperature evaporator 6-1, in a plurality of groups of low-pressure stage units, the second port of the second throttle valve 4-2 is connected with the second port of the medium-temperature evaporator 6-2 in parallel and is connected with the liquid outlet of the intercooler 3, the first port of the medium-temperature evaporator 6-2 is connected with the first air inlet of the intercooler 3 in parallel, the outlet of the first one-way valve 7-1 is connected with the second air inlet of the intercooler 3 after being connected with the outlet of the first one-way valve 7-1 in parallel, and the inlet of the second one-way valve 7-2 is connected with the air suction end of the high-pressure stage compressor unit and the air outlet of the intercooler 3 respectively; the exhaust end of the high-pressure stage compressor unit is connected with the liquid inlet of the intercooler 3 through the condenser 5 and the first throttle valve 4-1.
When the low-temperature evaporator in the low-pressure stage units does not need defrosting, all the low-pressure stage units are used for refrigeration circulation, namely all the low-pressure stage units realize refrigeration functions. In the low-pressure stage unit for realizing the refrigeration function, a first interface of the first four-way reversing valve 2-1 is connected with a fourth interface, and a second interface of the first four-way reversing valve 2-1 is connected with a third interface. The thermodynamic process of the secondary throttling middle full cooling two-stage compression refrigeration cycle with the medium temperature evaporator is as follows: in the low-pressure stage unit for realizing the refrigeration function, low-pressure vapor is sucked from the low-temperature evaporator 6-1 by the low-pressure stage compressor 1-1 through the first four-way reversing valve 2-1, working medium is compressed and boosted by the low-pressure stage compressor 1-1 and then is changed into medium-pressure superheated vapor, and then the medium-pressure superheated vapor is discharged into the intercooler 3 for cooling through the first four-way reversing valve 2-1, the first one-way valve 7-1 and the second air inlet 3-2 of the intercooler 3. The high-pressure stage compressor unit sucks medium-pressure saturated vapor from an air outlet 3-3 of the intercooler 3, the vapor is compressed and boosted by the high-pressure stage compressor unit to be changed into high-pressure superheated vapor, the high-pressure superheated vapor is discharged into the condenser 5 to be condensed into high-pressure liquid, the liquid is throttled and depressurized by the first throttle valve 4-1 to be changed into medium-pressure wet vapor, and the medium-pressure wet vapor enters the intercooler through a liquid inlet 3-4 of the intercooler 3; and a part of medium-pressure liquid working medium in the intercooler 3 is evaporated to absorb heat, and medium-pressure superheated steam entering through a second air inlet 3-2 of the intercooler is cooled. The medium-pressure saturated liquid working medium flowing out of the liquid outlet 3-5 of the intercooler is divided into two parts, one part of the medium-pressure saturated liquid working medium flowing out of the liquid outlet 3-5 of the intercooler is evaporated in the medium-temperature evaporator 6-2, heat in the medium-temperature refrigerator is absorbed, medium-temperature refrigeration phenomenon is generated, medium-pressure saturated vapor flowing out of the medium-temperature evaporator 6-2 returns to the intercooler through the first air inlet 3-1 of the intercooler 3, the other part of the medium-pressure saturated liquid working medium flowing out of the liquid outlet 3-5 of the intercooler is throttled and depressurized through the second throttle valve 4-2 to become low-pressure wet vapor, the low-pressure wet vapor enters the low-temperature evaporator 6-1 to be evaporated, heat in the low-temperature refrigerator is absorbed, low-temperature refrigeration phenomenon is generated, and the low-pressure vapor flowing out of the low-temperature evaporator 6-1 returns to the air suction end of the low-pressure stage compressor 1-1 through the first reversing valve 2-1, and the two-stage throttling, two-stage intermediate cooling and full compression refrigeration circulation with the medium-temperature evaporator is completed.
When the low-temperature evaporator in the low-pressure stage unit needs to defrost, the corresponding low-pressure stage unit realizes the defrosting function, and the rest low-pressure stage units realize the refrigerating function. The thermodynamic cycle process of the low-pressure stage unit for realizing the refrigeration function is unchanged. In the low-pressure stage unit for realizing the defrosting function, a first interface of the first four-way reversing valve 2-1 is connected with a second interface, and a third interface is connected with a fourth interface. In the low-pressure stage unit for realizing the refrigeration function, the first interface of the first four-way reversing valve 2-1 is connected with the fourth interface, and the second interface is connected with the third interface, so that the low-pressure stage compressor in the low-pressure stage unit for realizing the defrosting function is converted into the high-pressure stage compressor. In the low-pressure stage unit realizing the defrosting function, the defrosting thermodynamic process of the low-temperature evaporator 6-1 is as follows: the low-pressure stage compressor 1-1 sucks medium-pressure saturated vapor from the air outlet 3-3 of the intercooler through the first four-way reversing valve 2-1 and the second one-way valve 7-2, the vapor is compressed and boosted by the low-pressure stage compressor 1-1 and then becomes high-pressure superheated vapor, the high-pressure superheated vapor enters the low-temperature evaporator 6-1 through the first four-way reversing valve 2-1 to be condensed, the low-temperature evaporator 6-1 is heated, defrosting of the low-temperature evaporator 6-1 is realized, the condensed high-pressure liquid working medium is throttled and depressurized by the second throttle valve 4-2 to become medium-pressure wet vapor, the medium-pressure wet vapor is mixed with medium-pressure liquid flowing out from the liquid outlet 3-5 of the intercooler, and the mixed wet vapor enters the medium-temperature evaporators 6-2 corresponding to all low-pressure stage units respectively and the second throttle valves 4-2 corresponding to the low-pressure stage units realizing refrigeration functions, and the secondary throttling medium-stage refrigeration cycle with the medium-temperature evaporators is completed, and the secondary throttling medium-stage refrigeration cycle with the medium-temperature evaporators is completely cooled by adopting the heat pump cycle of the low-pressure stage compressor.
Example 2
The structural schematic diagram of the full-liquid type secondary throttling intermediate complete cooling refrigerating system for hot gas defrosting is shown in fig. 2, and comprises a high-pressure stage compressor unit, a condenser 5, a first throttling valve 4-1, an intercooler 3 and a plurality of groups of low-pressure stage units. In this embodiment, the high-pressure stage compressor unit includes one or more high-pressure stage compressors 1-2, and when a plurality of high-pressure stage compressors 1-2 are adopted, the air suction interface of each high-pressure stage compressor 1-2 is connected in parallel to serve as the air suction end of the high-pressure stage compressor unit, and the air discharge interface of each high-pressure stage compressor 1-2 is connected in parallel to serve as the air discharge end of the high-pressure stage compressor unit. The low-pressure stage units can be used for refrigeration cycle or defrosting cycle, each low-pressure stage unit comprises a low-pressure stage compressor 1-1, a first four-way reversing valve 2-1, a second four-way reversing valve 2-2, a second throttle valve 4-2, a low-temperature evaporator 6-1, a medium-temperature evaporator 6-2, a first one-way valve 7-1 and a second one-way valve 7-2, the air suction end of the low-pressure stage compressor 1-1 is connected with a fourth interface of the first four-way reversing valve 2-1, the air discharge end of the low-pressure stage compressor 1-1 is connected with a second interface of the first four-way reversing valve 2-1, a third interface of the first four-way reversing valve 2-1 is respectively connected with an inlet of the first one-way valve 7-1 and an outlet of the second one-way valve 7-2, the first interface of the first four-way reversing valve 2-1 is connected with the first interface of the second throttling valve 4-2 through the low-temperature evaporator 6-1, the second interface of the second throttling valve 4-2 is connected with the second interface of the second four-way reversing valve 2-2, the second interface of the medium-temperature evaporator 6-2 is connected with the third interface of the second four-way reversing valve 2-2, in a plurality of groups of low-pressure stage units, the first interfaces of the medium-temperature evaporators 6-2 are connected in parallel and are connected with the first air inlet 3-1 of the intercooler 3, and the first interface of the second four-way reversing valve 2-2 is connected in parallel with the fourth interface and is connected with the liquid outlet 3-5 of the intercooler 3; the outlet of the first one-way valve 7-1 is connected in parallel and connected with the second air inlet 3-2 of the intercooler 3, and the inlet of the second one-way valve 7-2 is connected in parallel and connected with the air suction end of the high-pressure stage compressor unit and the air outlet 3-3 of the intercooler 3 respectively; the exhaust end of the high-pressure stage compressor unit is connected with the liquid inlet 3-4 of the intercooler 3 through the condenser 5 and the first throttle valve 4-1.
When the low temperature evaporators 6-1 in all the low pressure stage units do not need defrosting, all the low pressure stage units are used for the refrigeration cycle, and the refrigeration function is realized. In the low-pressure stage unit for realizing the refrigeration function, a first interface of the first four-way reversing valve 2-1 is connected with a fourth interface, a second interface of the first four-way reversing valve 2-2 is connected with a third interface, and the first interface of the second four-way reversing valve 2-2 is connected with the second interface, and the third interface of the second four-way reversing valve is connected with the fourth interface. The thermodynamic process of the secondary throttling middle full cooling two-stage compression refrigeration cycle with the medium temperature evaporator is as follows: in the low-pressure stage unit for realizing the refrigeration function, a low-pressure stage compressor 1-1 sucks low-pressure steam from the low-temperature evaporator 6-1 through the first four-way reversing valve 2-1, working medium is compressed and boosted by the low-pressure stage compressor 1-1 and then is changed into medium-pressure superheated steam, and then the medium-pressure superheated steam is discharged into the intercooler 3 for cooling through the first four-way reversing valve 2-1, the first one-way valve 7-1 and the second air inlet 3-2 of the intercooler 3; the high-pressure stage compressor 1-2 in the high-pressure stage compressor unit sucks medium-pressure saturated vapor from the air outlet 3-3 of the intercooler 3, the vapor is compressed and boosted by the high-pressure stage compressor 1-2 to become high-pressure superheated vapor, the high-pressure superheated vapor enters the condenser 5 and is condensed into high-pressure liquid, the high-pressure liquid is throttled and depressurized by the first throttle valve 4-1 to become medium-pressure wet vapor, and the medium-pressure wet vapor enters the intercooler 3 through the liquid inlet 3-4 of the intercooler 3; and a part of medium-pressure liquid working medium in the intercooler 3 is evaporated to absorb heat, and medium-pressure superheated steam entering through a second air inlet 3-2 of the intercooler 3 is cooled. The medium-pressure saturated liquid working medium flowing out of the liquid outlet 3-5 of the intercooler 3 is divided into two parts, one part of medium-pressure saturated liquid working medium enters the medium-temperature evaporator 6-2 through the second four-way reversing valve 2-2 to be evaporated, absorbs heat in the medium-temperature refrigeration house to generate a medium-temperature refrigeration phenomenon, and medium-pressure saturated vapor flowing out of the medium-temperature evaporator 6-2 returns to the intercooler 3 through the first air inlet 3-1 of the intercooler 3; the other part of medium-pressure saturated liquid working medium from the liquid outlet 3-5 of the intercooler 3 enters the second throttle valve 4-2 through the second four-way reversing valve 2-2, throttles and reduces pressure through the second throttle valve 4-2 to become low-pressure wet vapor, the low-pressure wet vapor enters the low-temperature evaporator 6-1 to evaporate, absorbs heat in the low-temperature refrigerator, generates a low-temperature refrigeration phenomenon, and the low-pressure vapor from the low-temperature evaporator 6-1 returns to the air suction end of the low-pressure compressor 1-1 through the first four-way reversing valve 2-1 to complete the secondary throttling middle complete cooling two-stage compression refrigeration cycle with the medium-temperature evaporator.
When the low-temperature evaporator in the low-pressure stage unit needs to defrost, the corresponding low-pressure stage unit realizes the defrosting function, and the rest low-pressure stage units realize the refrigerating function. The connection interface of the first four-way reversing valve 2-1 and the second four-way reversing valve 2-2 in the low-pressure stage unit for realizing the refrigeration function is unchanged in the thermodynamic cycle process. In the low-pressure stage unit for realizing the defrosting function, the first interface of the first four-way reversing valve 2-1 is connected with the second interface, the third interface is connected with the fourth interface, and the first interface of the second four-way reversing valve 2-2 is connected with the fourth interface, and the second interface is connected with the third interface, so that the low-pressure stage compressor in the low-pressure stage unit for realizing the defrosting function is converted into the high-pressure stage compressor. The defrosting thermodynamic process of the low-temperature evaporator in the low-pressure stage unit for realizing the defrosting function is as follows: in the low-pressure stage unit for realizing the defrosting function, the low-pressure stage compressor 1-1 sucks medium-pressure saturated vapor from the air outlet 3-3 of the intercooler 3 through the first four-way reversing valve 2-1 and the second one-way valve 7-2, the vapor is compressed and boosted by the low-pressure stage compressor 1-1 and then is changed into high-pressure superheated vapor, the high-pressure superheated vapor is discharged into the low-temperature evaporator 6-1 to be condensed, the low-temperature evaporator 6-1 is heated to generate the defrosting phenomenon of the low-temperature evaporator 6-1, the high-pressure liquid working medium which is condensed is throttled and depressurized by the second throttle valve 4-2 to become medium-pressure wet vapor, the wet vapor enters the medium-temperature evaporator 6-2 through the second four-way reversing valve 2-2 to be evaporated, and the two-stage compression refrigeration cycle with full cooling and double-stage compression refrigeration cycle with the medium-temperature evaporator is completed, wherein the medium-temperature evaporator is used for defrosting by the heat pump cycle of the low-pressure stage compressor.
Example 3
The structural schematic diagram of the non-flooded secondary throttling intermediate complete cooling refrigerating system for defrosting high-temperature hot air is shown in fig. 3, and comprises a high-pressure stage compressor unit, a condenser 5, a first throttling valve 4-1, an intercooler 3, a third four-way reversing valve 2-3 and a plurality of low-pressure stage units. In this embodiment, the high-pressure stage compressor unit includes one or more high-pressure stage compressors 1-2, and when a plurality of high-pressure stage compressors 1-2 are adopted, the air suction interface of each high-pressure stage compressor 1-2 is connected in parallel to serve as the air suction end of the high-pressure stage compressor unit, and the air discharge interface of each high-pressure stage compressor 1-2 is connected in parallel to serve as the air discharge end of the high-pressure stage compressor unit. The low-pressure stage units can be used for refrigeration cycle or defrosting cycle, each low-pressure stage unit comprises a low-pressure stage compressor 1-1, a first four-way reversing valve 2-1, a second throttle valve 4-2, a low-temperature evaporator 6-1, a medium-temperature evaporator 6-2, a first one-way valve 7-1 and a second one-way valve 7-2, wherein the air suction end of the low-pressure stage compressor 1-1 is connected with a fourth interface of the first four-way reversing valve 2-1, the air discharge end of the low-pressure stage compressor 1-1 is connected with a second interface of the first four-way reversing valve 2-1, a third interface of the first four-way reversing valve 2-1 is connected with an inlet of the first one-way valve 7-1 and an outlet of the second one-way valve 7-2 respectively, and the first interface of the first four-way reversing valve 2-1 is connected with a first interface of the second throttle valve 4-2 through the low-temperature evaporator 6-1; in the low-pressure stage units, a first interface of the intermediate-temperature evaporator 6-2 is connected in parallel and connected with a first air inlet 3-1 of the intermediate cooler 3, a second interface of the second throttle valve 4-2 is connected in parallel and connected with a second interface of the intermediate-temperature evaporator 6-2 and connected with a liquid outlet 3-5 of the intermediate cooler 3, an outlet of the first one-way valve 7-1 is connected in parallel and connected with a second interface of the third four-way reversing valve 2-3, an inlet of the second one-way valve 7-2 is connected in parallel and connected with an air suction end of the high-pressure stage compressor unit and a third interface of the third four-way reversing valve 2-3 respectively, a first interface of the third four-way reversing valve 2-3 is connected with the second air inlet 3-2 of the intermediate cooler 3, and a fourth interface of the third four-way reversing valve 2-3 is connected with an air outlet 3-3 of the intermediate cooler 3; the exhaust end of the high-pressure stage compressor unit is connected with the liquid inlet 3-4 of the intercooler 3 through the condenser 5 and the first throttle valve 4-1.
When the low-temperature evaporator in the low-pressure stage units does not need defrosting, all the low-pressure stage units are used for refrigeration circulation, and the refrigeration function is realized. The first interface of the third four-way reversing valve 2-3 is connected with the second interface, and the third interface is connected with the fourth interface. In the low-pressure stage unit for realizing the refrigeration function, a first interface of the first four-way reversing valve 2-1 is connected with a fourth interface, and a second interface is connected with a third interface. The thermodynamic process of the secondary throttling middle full cooling two-stage compression refrigeration cycle with the medium temperature evaporator is as follows: in the low-pressure stage unit for realizing the refrigeration function, the low-pressure stage compressor 1-1 sucks low-pressure steam from the low-temperature evaporator 6-1 through the first four-way reversing valve 2-1, working medium is compressed and boosted by the low-pressure stage compressor 1-1 and then becomes medium-pressure superheated steam, and then the medium-pressure superheated steam enters the intercooler 3 for cooling through the first four-way reversing valve 2-1, the first one-way valve 7-1, the third four-way reversing valve 2-3 and the second air inlet 3-2 of the intercooler 3. The high-pressure stage compressor 1-2 in the high-pressure stage compressor unit sucks medium-pressure saturated vapor from the air outlet 3-3 of the intercooler 3 through a third four-way reversing valve 2-3, the vapor is compressed and boosted through the high-pressure stage compressor 1-2 to become high-pressure superheated vapor, the high-pressure superheated vapor enters the condenser 5 and is condensed into high-pressure liquid, the high-pressure liquid is throttled and depressurized through the first throttle valve 4-1 to become medium-pressure wet vapor, and the medium-pressure wet vapor enters the intercooler 3 through the liquid inlet 3-4 of the intercooler 3; and a part of medium-pressure liquid working medium in the intercooler 3 is evaporated to absorb heat, and medium-pressure superheated steam entering through a second air inlet 3-2 of the intercooler 3 is cooled. The medium-pressure saturated liquid working medium which comes out from the liquid outlet 3-5 of the intercooler 3 is divided into two parts, one part of medium-pressure saturated liquid working medium enters the medium-temperature evaporator 6-2 to be evaporated, absorbs heat in the medium-temperature refrigeration house to generate a medium-temperature refrigeration phenomenon, and medium-pressure saturated vapor which comes out from the medium-temperature evaporator 6-2 returns to the intercooler 3 through the first air inlet 3-1 of the intercooler 3; the other part of medium-pressure saturated liquid working medium is throttled and depressurized by the second throttle valve 4-2 to become low-pressure wet vapor, the low-pressure wet vapor enters the low-temperature evaporator 6-1 to be evaporated, heat in a low-temperature refrigeration house is absorbed, a low-temperature refrigeration phenomenon is generated, the low-pressure vapor coming out of the low-temperature evaporator 6-1 returns to the air suction end of the low-pressure compressor 1-1 by the first four-way reversing valve 2-1, and the secondary throttling middle full cooling two-stage compression refrigeration cycle with the medium-temperature evaporator is completed.
When the low-temperature evaporator in the low-pressure stage units needs to defrost, the corresponding low-pressure stage units are defrost cycles, so that the defrosting function is realized, and the rest low-pressure stage units are refrigeration cycles, so that the refrigeration function is realized. The connection interface of the first four-way reversing valve in the low-pressure stage unit for realizing the refrigeration function is unchanged in the refrigeration thermodynamic cycle process. The first interface of the third four-way reversing valve 2-3 is connected with the fourth interface, and the second interface is connected with the third interface. In the low-pressure stage unit for realizing the defrosting function, the first interface of the first four-way reversing valve 2-1 is connected with the second interface, and the third interface is connected with the fourth interface, so that the low-pressure stage compressor in the low-pressure stage unit for realizing the defrosting function is converted into the high-pressure stage compressor. The defrosting thermodynamic process of the low-temperature evaporator in the defrosting low-pressure stage unit is as follows: in the low-pressure stage unit realizing the defrosting function, the low-pressure stage compressor 1-1 sucks medium-pressure superheated steam from the exhaust end of the low-pressure stage compressor of the low-pressure stage unit realizing the refrigerating function through the first four-way reversing valve 2-1, the second one-way valve 7-2 and the third four-way reversing valve 2-3, the steam is compressed and boosted through the low-pressure stage compressor of the low-pressure stage unit realizing the defrosting function and then is changed into high-pressure superheated steam to be discharged into the low-temperature evaporator 6-1 for condensation, the low-temperature evaporator 6-1 is heated, the defrosting phenomenon of the low-temperature evaporator 6-1 is generated, the condensed high-pressure liquid working medium is throttled by the second throttle valve 4-2 and becomes medium-pressure wet steam to be mixed with medium-pressure liquid coming out of the liquid outlet 3-5 of the intermediate cooler 3, the medium-temperature evaporator 6-2 of all the low-pressure stage unit and the second throttle valve 4-2 in the low-pressure stage unit realizing the refrigerating function are respectively mixed into wet steam, the medium-temperature evaporator 6-2 enters the low-temperature evaporator 6-2, the first low-temperature evaporator and the low-temperature evaporator 3 is cooled through the first low-temperature evaporator and the low-temperature evaporator with the low-temperature condenser, and the medium-temperature low-temperature evaporator 3 is completely cooled, and the medium-temperature compressed and discharged into the medium-temperature evaporator 3 is completely cooled, and the medium-temperature evaporator is completely cooled, and the medium-pressure medium-grade steam is cooled, and the medium-grade low-grade steam.
Example 4
The structural schematic diagram of the flooded secondary throttling intermediate complete cooling refrigerating system for defrosting high-temperature hot air is shown in fig. 4, and comprises a high-pressure stage compressor unit, a condenser 5, a first throttling valve 4-1, a third four-way reversing valve 2-3, an intercooler 3 and a plurality of low-pressure stage units. In this embodiment, the high-pressure stage compressor unit includes one or more high-pressure stage compressors 1-2, and when a plurality of high-pressure stage compressors 1-2 are adopted, the air suction interface of each high-pressure stage compressor 1-2 is connected in parallel to serve as the air suction end of the high-pressure stage compressor unit, and the air discharge interface of each high-pressure stage compressor 1-2 is connected in parallel to serve as the air discharge end of the high-pressure stage compressor unit. The low-pressure stage units can be used for refrigeration cycle or defrosting cycle, each low-pressure stage unit comprises a low-pressure stage compressor 1-1, a first four-way reversing valve 2-1, a second four-way reversing valve 2-2, a second throttle valve 4-2, a low-temperature evaporator 6-1, a medium-temperature evaporator 6-2, a first one-way valve 7-1 and a second one-way valve 7-2, the suction end of the low-pressure stage compressor 1-1 is connected with a fourth interface of the first four-way reversing valve 2-1, the discharge end of the low-pressure stage compressor 1-1 is connected with a second interface of the first four-way reversing valve 2-1, a third interface of the first four-way reversing valve 2-1 is connected with an inlet of the first one-way valve 7-1 and an outlet of the second one-way valve 7-2 respectively, a first interface of the first four-way reversing valve 2-1 is connected with a first interface of the second throttle valve 4-2 through the low-temperature evaporator 6-1, and a second interface of the second four-way reversing valve 4-2 is connected with a second interface of the four-way reversing valve 2-2; the first interface of the intermediate temperature evaporator 6-2 is connected in parallel and connected with the first air inlet 3-1 of the intercooler 3, the other end of the intermediate temperature evaporator 6-2 is connected with the third interface of the second four-way reversing valve 2-2, and the first interface and the fourth interface of the second four-way reversing valve 2-2 are connected in parallel and connected with the liquid outlet 3-5 of the intercooler 3; the outlet of the first one-way valve 7-1 is connected in parallel and connected with the second interface of the third four-way reversing valve 2-3, the inlet of the second one-way valve 7-2 is connected in parallel and connected with the suction end of the high-pressure stage compressor unit and the third interface of the third four-way reversing valve 2-3 respectively, the first interface of the third four-way reversing valve 2-3 is connected with the second air inlet 3-2 of the intercooler 3, and the fourth interface of the third four-way reversing valve 2-3 is connected with the air outlet 3-3 of the intercooler 3; the exhaust end of the high-pressure stage compressor unit is connected with the liquid inlet 3-4 of the intercooler 3 through the condenser 5 and the first throttle valve 4-1.
When the low-temperature evaporator in the low-pressure stage units does not need defrosting, all the low-pressure stage units are used for refrigeration circulation, namely all the low-pressure stage units realize refrigeration functions. The first interface and the second interface of the third four-way reversing valve 2-3 are connected, the third interface and the fourth interface are connected, the first interface and the fourth interface of the first four-way reversing valve 2-1 are connected, the second interface and the third interface are connected, and the first interface and the second interface of the second four-way reversing valve 2-2 are connected, and the third interface and the fourth interface are connected. The thermodynamic process of the secondary throttling middle full cooling two-stage compression refrigeration cycle with the medium temperature evaporator is as follows: the low-pressure stage compressor 1-1 sucks low-pressure steam from the low-temperature evaporator 6-1 through the first four-way reversing valve 2-1, working medium is compressed and boosted through the low-pressure stage compressor 1-1 and then becomes medium-pressure superheated steam, and then the medium-pressure superheated steam is discharged into the intercooler 3 for cooling through the first four-way reversing valve 2-1, the first one-way valve 7-1, the third four-way reversing valve 2-3 and the second air inlet 3-2 of the intercooler 3; the high-pressure stage compressors 1-2 in the high-pressure stage compression group absorb medium-pressure saturated vapor from the air outlet 3-3 of the intercooler 3 through the third four-way reversing valve 2-3, the vapor is compressed and boosted through the high-pressure stage compressors 1-2 to be changed into high-pressure superheated vapor, the high-pressure superheated vapor is discharged into the condenser 5 to be condensed into high-pressure liquid, the high-pressure liquid is throttled and depressurized through the first throttle valve 4-1 to be changed into medium-pressure wet vapor, and the medium-pressure wet vapor enters the intercooler 3 through the liquid inlet 3-4 of the intercooler 3. And a part of medium-pressure liquid working medium in the intercooler 3 is evaporated to absorb heat, and medium-pressure superheated steam entering through a second air inlet 3-2 of the intercooler 3 is cooled. The medium-pressure saturated liquid working medium which comes out from the liquid outlet 3-5 of the intercooler 3 is divided into two parts, one part of medium-pressure saturated liquid working medium enters the medium-temperature evaporator 6-2 through the second four-way reversing valve 2-2 to be evaporated, absorbs heat in the medium-temperature refrigeration house to generate a medium-temperature refrigeration phenomenon, and medium-pressure saturated vapor which comes out from the medium-temperature evaporator 6-2 returns to the intercooler 3 through the first air inlet 3-1 of the intercooler 3; the other part of medium-pressure saturated liquid working medium from the liquid outlet 3-5 of the intercooler 3 is throttled and depressurized by the second four-way reversing valve 2-2 and the second throttle valve 4-2 to become low-pressure wet vapor, the low-pressure wet vapor enters the low-temperature evaporator 6-1 to be evaporated, the heat in the low-temperature refrigeration house is absorbed, the low-temperature refrigeration phenomenon is generated, the low-pressure vapor from the low-temperature evaporator 6-1 returns to the air suction end of the low-pressure stage compressor 1-1 by the first four-way reversing valve 2-1, and the secondary throttle middle complete cooling two-stage compression refrigeration cycle with the medium-temperature evaporator is completed.
When the low-temperature evaporator in the low-pressure stage unit needs to defrost, the corresponding low-pressure stage unit realizes the defrosting function, and the rest low-pressure stage units realize the refrigerating function. The connection interface of the first four-way reversing valve and the second four-way reversing valve in the low-pressure stage unit for realizing the refrigeration function is unchanged in thermodynamic cycle. The first interface of the third four-way reversing valve 2-3 is connected with the fourth interface, and the second interface is connected with the third interface. In the defrosting low-pressure stage unit, a first interface of the first four-way reversing valve 2-1 is connected with a second interface, a third interface is connected with a fourth interface, and the first interface of the second four-way reversing valve 2-2 is connected with the fourth interface, and the second interface is connected with the third interface, so that a low-pressure stage compressor in the low-pressure stage unit for realizing the defrosting function is converted into a high-pressure stage compressor. The defrosting thermodynamic process of the low-temperature evaporator in the defrosting low-pressure stage unit is as follows: the low-pressure stage compressor 1-1 in the defrosting low-pressure stage unit sucks medium-pressure overheat steam from the exhaust end of the low-pressure stage compressor 1-1 of the low-pressure stage unit realizing the refrigerating function through the first four-way reversing valve 2-1, the second one-way valve 7-2 and the third four-way reversing valve 2-3, the steam is compressed and boosted by the low-pressure stage compressor 1-1 and then becomes high-pressure overheat steam to be discharged into the low-temperature evaporator 6-1 for condensation, the low-temperature evaporator 6-1 is heated to generate the defrosting phenomenon of the low-temperature evaporator 6-1, the condensed high-pressure liquid working medium is throttled and depressurized by the second throttle valve 4-2 to become medium-pressure wet steam, the wet steam enters the medium-temperature evaporator 6-2 of the low-pressure stage unit realizing the defrosting function through the second four-way reversing valve 2-2 and then enters the intermediate-temperature evaporator 3 through the first air inlet 3-1 of the intermediate cooler together with the working medium discharged by the medium-temperature evaporator in the low-pressure stage unit realizing the refrigerating function, and the two-stage low-temperature evaporator discharged by the low-pressure stage compressor is completely cooled by the aid of the second throttle valve 2-stage compressor.
The low-temperature compressor and the high-temperature compressor can be any one of a scroll compressor, a rotor compressor, a screw compressor and a piston compressor.
The condenser is an air-cooled condenser, a water-cooled condenser or an evaporative condenser.
The evaporator is air-cooled or solution-cooled.
The intercooler is a plate heat exchanger, a sleeve heat exchanger or a shell-and-tube heat exchanger.
The first throttle valve and the second throttle valve are electronic expansion valves, thermal expansion valves, capillary tubes or orifice plate throttle devices.
The first one-way valve, the second one-way valve, the first four-way reversing valve, the second four-way reversing valve and the third four-way reversing valve are in the prior art, and can be replaced by an electromagnetic valve, a hand valve and a three-way reversing valve in the system.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims (6)

1. The operation method of the two-stage compression refrigerating system with the secondary throttling and the middle complete cooling is characterized in that the refrigerating system comprises a high-pressure stage compressor set, a condenser, a first throttling valve, an intercooler and a plurality of low-pressure stage units; each low-pressure stage unit comprises a low-pressure stage compressor, a first four-way reversing valve, a second throttling valve, a low-temperature evaporator, a middle-temperature evaporator, a first one-way valve and a second one-way valve, wherein the air suction end of the low-pressure stage compressor is connected with the fourth interface of the first four-way reversing valve, the air discharge end of the low-pressure stage compressor is connected with the second interface of the first four-way reversing valve, the third interface of the first four-way reversing valve is respectively connected with the inlet of the first one-way valve and the outlet of the second one-way valve, the first interface of the first four-way reversing valve is connected with the first interface of the second throttling valve through the low-temperature evaporator, the second interface of the second throttling valve is connected with the second interface of the middle-temperature evaporator in parallel and is connected with the liquid outlet of the middle-temperature evaporator, the first interface of the middle-temperature evaporator is connected with the first interface of the middle-temperature evaporator in parallel and is connected with the first air inlet of the middle-temperature evaporator, the first interface of the first four-way reversing valve is connected with the first air inlet of the middle-temperature evaporator in parallel and the air inlet of the middle-temperature evaporator is connected with the air inlet of the middle-pressure stage unit in parallel and the high-pressure stage unit in parallel; the exhaust end of the high-pressure stage compressor unit is connected with the liquid inlet of the intercooler through the condenser and the first throttle valve, the medium-temperature evaporator and the low-temperature evaporator are arranged in each low-pressure stage unit, the medium-temperature evaporator is used for realizing medium-temperature refrigeration, and the low-temperature evaporator is used for realizing low-temperature refrigeration or defrosting, and the operation method comprises the following steps: when all low-pressure units realize the refrigeration function, the medium-temperature evaporator evaporates medium-pressure saturated liquid working medium into medium-pressure saturated vapor to realize medium-temperature refrigeration; the low-temperature evaporator evaporates the low-pressure liquid working medium into low-pressure vapor to realize low-temperature refrigeration; when the low-temperature evaporator needs defrosting, the low-pressure stage compressor realizing the defrosting function is converted into a high-pressure stage compressor to operate through valve switching, the low-pressure stage compressor in the low-pressure stage unit realizing the defrosting function absorbs medium-pressure superheated steam from the low-pressure stage compressor realizing the refrigerating function or medium-pressure saturated steam from the intercooler, and the medium-pressure superheated steam is compressed and then sent into the low-temperature evaporator to be defrosted, so that the low-temperature evaporator is condensed and heated, defrosting is realized, and the low-temperature evaporator in the low-pressure stage unit realizing the refrigerating function still realizes the refrigerating function; after defrosting is finished, the low-pressure stage unit for realizing the defrosting function is switched by a valve to realize the refrigerating function.
2. The method of operation of claim 1, wherein the high-pressure stage compressor package comprises one or more high-pressure stage compressors, and when a plurality of high-pressure stage compressors are employed, a suction port of each high-pressure stage compressor is connected in parallel as a suction port of the high-pressure stage compressor package, and a discharge port of each high-pressure stage compressor is connected in parallel as a discharge port of the high-pressure stage compressor package.
3. The method of operation of claim 2, wherein the number of low pressure stage units is at least three.
4. A method of operating a secondary throttled intercooling refrigeration system, the refrigeration system comprising a high pressure stage compressor train, a condenser, a first throttle valve, an intercooler and a plurality of low pressure stage units; each low-pressure stage unit comprises a low-pressure stage compressor, a first four-way reversing valve, a second throttle valve, a low-temperature evaporator, a middle-temperature evaporator, a first one-way valve and a second one-way valve, wherein the air suction end of the low-pressure stage compressor is connected with the fourth interface of the first four-way reversing valve, the air discharge end of the low-pressure stage compressor is connected with the second interface of the first four-way reversing valve, the third interface of the first four-way reversing valve is respectively connected with the inlet of the first one-way valve and the outlet of the second one-way valve, the first interface of the first four-way reversing valve is connected with the first interface of the second throttle valve through the low-temperature evaporator, the second interface of the second throttle valve is connected with the second interface of the second four-way reversing valve, the second interface of the middle-temperature evaporator is connected with the third interface of the second four-way reversing valve, and in a plurality of low-pressure stage units, the first interface of the middle-temperature evaporator is connected with the fourth interface of the fourth four-way reversing valve in parallel and is connected with the first interface of the middle-temperature evaporator and the fourth interface of the middle-temperature evaporator is connected with the fourth interface of the middle-temperature reversing valve in parallel; the outlet of the first one-way valve is connected in parallel and connected with the second air inlet of the intercooler, and the inlet of the second one-way valve is connected in parallel and connected with the air suction end of the high-pressure stage compressor unit and the air outlet of the intercooler respectively; the exhaust end of the high-pressure stage compressor unit is connected with the liquid inlet of the intercooler through the condenser and the first throttle valve; the low-pressure stage units are provided with a medium-temperature evaporator and a low-temperature evaporator, the medium-temperature evaporator is used for realizing medium-temperature refrigeration, the low-temperature evaporator is used for realizing low-temperature refrigeration or defrosting, and the operation method comprises the following steps: when all low-pressure units realize the refrigeration function, the medium-temperature evaporator evaporates medium-pressure saturated liquid working medium into medium-pressure saturated vapor to realize medium-temperature refrigeration; the low-temperature evaporator evaporates the low-pressure liquid working medium into low-pressure vapor to realize low-temperature refrigeration; when the low-temperature evaporator needs defrosting, the low-pressure stage compressor realizing the defrosting function is converted into a high-pressure stage compressor to operate through valve switching, the low-pressure stage compressor in the low-pressure stage unit realizing the defrosting function absorbs medium-pressure superheated steam from the low-pressure stage compressor realizing the refrigerating function or medium-pressure saturated steam from the intercooler, and the medium-pressure superheated steam is compressed and then sent into the low-temperature evaporator to be defrosted, so that the low-temperature evaporator is condensed and heated, defrosting is realized, and the low-temperature evaporator in the low-pressure stage unit realizing the refrigerating function still realizes the refrigerating function; after defrosting is finished, the low-pressure stage unit for realizing the defrosting function is switched by a valve to realize the refrigerating function.
5. The operation method of the secondary throttling and intermediate complete cooling refrigerating system is characterized in that the refrigerating system comprises a high-pressure stage compressor unit, a condenser, a first throttling valve, an intermediate cooler, a third four-way reversing valve and a plurality of low-pressure stage units; each low-pressure stage unit comprises a low-pressure stage compressor, a first four-way reversing valve, a second throttle valve, a low-temperature evaporator, a medium-temperature evaporator, a first one-way valve and a second one-way valve, wherein the air suction end of the low-pressure stage compressor is connected with a fourth interface of the first four-way reversing valve, the air discharge end of the low-pressure stage compressor is connected with a second interface of the first four-way reversing valve, a third interface of the first four-way reversing valve is connected with an inlet of the first one-way valve and an outlet of the second one-way valve respectively, and the first interface of the first four-way reversing valve is connected with a first interface of the second throttle valve through the low-temperature evaporator; in the low-pressure stage units, a first interface of the intermediate-temperature evaporator is connected in parallel and connected with a first air inlet of the intercooler, a second interface of the second throttle valve is connected in parallel with a second interface of the intermediate-temperature evaporator and connected with a liquid outlet of the intercooler, an outlet of the first one-way valve is connected in parallel and connected with a second interface of the third four-way reversing valve, an inlet of the second one-way valve is connected in parallel and connected with an air suction end of the high-pressure stage compressor unit and a third interface of the third four-way reversing valve respectively, the first interface of the third four-way reversing valve is connected with a second air inlet of the intercooler, and a fourth interface of the third four-way reversing valve is connected with an air outlet of the intercooler; the exhaust end of the high-pressure stage compressor unit is connected with the liquid inlet of the intercooler through the condenser and the first throttle valve; the low-pressure stage units are provided with a medium-temperature evaporator and a low-temperature evaporator, the medium-temperature evaporator is used for realizing medium-temperature refrigeration, the low-temperature evaporator is used for realizing low-temperature refrigeration or defrosting, and the operation method comprises the following steps: when all low-pressure units realize the refrigeration function, the medium-temperature evaporator evaporates medium-pressure saturated liquid working medium into medium-pressure saturated vapor to realize medium-temperature refrigeration; the low-temperature evaporator evaporates the low-pressure liquid working medium into low-pressure vapor to realize low-temperature refrigeration; when the low-temperature evaporator needs defrosting, the low-pressure stage compressor realizing the defrosting function is converted into a high-pressure stage compressor to operate through valve switching, the low-pressure stage compressor in the low-pressure stage unit realizing the defrosting function absorbs medium-pressure superheated steam from the low-pressure stage compressor realizing the refrigerating function or medium-pressure saturated steam from the intercooler, and the medium-pressure superheated steam is compressed and then sent into the low-temperature evaporator to be defrosted, so that the low-temperature evaporator is condensed and heated, defrosting is realized, and the low-temperature evaporator in the low-pressure stage unit realizing the refrigerating function still realizes the refrigerating function; after defrosting is finished, the low-pressure stage unit for realizing the defrosting function is switched by a valve to realize the refrigerating function.
6. The operation method of the secondary throttling and intermediate complete cooling refrigerating system is characterized in that the refrigerating system comprises a high-pressure stage compressor unit, a condenser, a first throttle valve, a third four-way reversing valve, an intermediate cooler and a plurality of low-pressure stage units; each low-pressure stage unit comprises a low-pressure stage compressor, a first four-way reversing valve, a second throttle valve, a low-temperature evaporator, a medium-temperature evaporator, a first one-way valve and a second one-way valve, wherein the air suction end of the low-pressure stage compressor is connected with a fourth interface of the first four-way reversing valve, the air discharge end of the low-pressure stage compressor is connected with a second interface of the first four-way reversing valve, a third interface of the first four-way reversing valve is connected with an inlet of the first one-way valve and an outlet of the second one-way valve respectively, the first interface of the first four-way reversing valve is connected with the first interface of the second throttle valve through the low-temperature evaporator, and the second interface of the second throttle valve is connected with the second interface of the second four-way reversing valve; the first interface of the intermediate temperature evaporator is connected in parallel and connected with the first air inlet of the intercooler, the other end of the intermediate temperature evaporator is connected with the third interface of the second four-way reversing valve, and the first interface and the fourth interface of the second four-way reversing valve are connected in parallel and connected with the liquid outlet of the intercooler; the outlet of the first one-way valve is connected in parallel and connected with the second interface of the third four-way reversing valve, the inlet of the second one-way valve is connected in parallel and connected with the suction end of the high-pressure stage compressor unit and the third interface of the third four-way reversing valve respectively, the first interface of the third four-way reversing valve is connected with the second air inlet of the intercooler, and the fourth interface of the third four-way reversing valve is connected with the air outlet of the intercooler; the exhaust end of the high-pressure stage compressor unit is connected with the liquid inlet of the intercooler through the condenser and the first throttle valve; the low-pressure stage units are provided with a medium-temperature evaporator and a low-temperature evaporator, the medium-temperature evaporator is used for realizing medium-temperature refrigeration, the low-temperature evaporator is used for realizing low-temperature refrigeration or defrosting, and the operation method comprises the following steps: when all low-pressure units realize the refrigeration function, the medium-temperature evaporator evaporates medium-pressure saturated liquid working medium into medium-pressure saturated vapor to realize medium-temperature refrigeration; the low-temperature evaporator evaporates the low-pressure liquid working medium into low-pressure vapor to realize low-temperature refrigeration; when the low-temperature evaporator needs defrosting, the low-pressure stage compressor realizing the defrosting function is converted into a high-pressure stage compressor to operate through valve switching, the low-pressure stage compressor in the low-pressure stage unit realizing the defrosting function absorbs medium-pressure superheated steam from the low-pressure stage compressor realizing the refrigerating function or medium-pressure saturated steam from the intercooler, and the medium-pressure superheated steam is compressed and then sent into the low-temperature evaporator to be defrosted, so that the low-temperature evaporator is condensed and heated, defrosting is realized, and the low-temperature evaporator in the low-pressure stage unit realizing the refrigerating function still realizes the refrigerating function; after defrosting is finished, the low-pressure stage unit for realizing the defrosting function is switched by a valve to realize the refrigerating function.
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