CN115046324A - Refrigerating system and circulating defrosting method of evaporator - Google Patents
Refrigerating system and circulating defrosting method of evaporator Download PDFInfo
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- CN115046324A CN115046324A CN202210082103.1A CN202210082103A CN115046324A CN 115046324 A CN115046324 A CN 115046324A CN 202210082103 A CN202210082103 A CN 202210082103A CN 115046324 A CN115046324 A CN 115046324A
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- evaporator
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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
- F25B5/00—Compression machines, plants or systems, with several evaporator circuits, e.g. for varying refrigerating capacity
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B41/00—Fluid-circulation arrangements
- F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B41/00—Fluid-circulation arrangements
- F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
- F25B41/24—Arrangement of shut-off valves for disconnecting a part of the refrigerant cycle, e.g. an outdoor part
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B41/00—Fluid-circulation arrangements
- F25B41/40—Fluid line arrangements
- F25B41/42—Arrangements for diverging or converging flows, e.g. branch lines or junctions
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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
- F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
- F25B47/02—Defrosting cycles
- F25B47/022—Defrosting cycles hot gas defrosting
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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
- F25B2500/00—Problems to be solved
- F25B2500/28—Means for preventing liquid refrigerant entering into the compressor
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Defrosting Systems (AREA)
- Compression-Type Refrigeration Machines With Reversible Cycles (AREA)
Abstract
The invention relates to a refrigeration system and an evaporator circulating defrosting method, belonging to the technical field of refrigeration. During refrigeration, refrigerant vapor from the compressor releases heat in the condenser to become refrigerant liquid, the refrigerant liquid is stored in the liquid storage device and then is introduced into the evaporation branch, the pressure is reduced after passing through the throttling mechanism, the refrigerant liquid is subjected to heat absorption and gasification in the evaporator to become low-pressure refrigerant gas, and the low-pressure refrigerant gas is pumped into the compressor to perform the next cycle of refrigeration cycle. When defrosting is carried out, a defrosting port above the liquid level of the liquid storage device is communicated with the evaporator through the gating device, refrigerant gas is formed above the refrigerant liquid stored in the liquid storage device, and the refrigerant gas is introduced into the evaporator to release heat and defrost. Compared with the refrigerant gas output by the compressor, the temperature of the part of refrigerant gas is lower, the temperature difference between the part of refrigerant gas and the frost layer on the evaporator is small, and the probability of liquid hammer and liquid explosion is effectively reduced.
Description
Technical Field
The invention relates to a refrigeration system and an evaporator circulating defrosting method, belongs to the technical field of refrigeration, and particularly relates to circulating defrosting of a refrigeration system with a plurality of evaporators.
Background
In general, the temperature of the evaporator surface of a refrigeration system is lower than 0 ℃, and water vapor in the air is separated from the air and freezes on the cold surface to become frost crystals, thereby further forming a frost layer. Frost is a poor conductor of heat and weakens the heat transfer of the heat exchanger, so the evaporator should be defrosted periodically. Common defrosting methods for evaporators include refrigeration cycle off defrosting, manual defrosting, electric heating defrosting, water defrosting, hot gas + water defrosting, and the like.
The refrigeration cycle stopping defrosting is only suitable for occasions with the refrigeration space temperature higher than 0 ℃ and low requirement on the refrigeration space temperature stability; the labor intensity of manual frost sweeping is high, the working environment condition is severe, and the defrosting effect is general, namely, the frost layer of the evaporator is difficult to be removed completely; the energy consumption of electric heating defrosting is large, the time of electric heating defrosting is generally long, the influence on the temperature of a refrigerating space is large, and the condition that the temperature fluctuation of the refrigerating space is large easily occurs; the water defrosting process often causes spray water to overflow or splash from the water receiving tray, and the fogging phenomenon is caused by higher water temperature; the hot gas defrosting has the advantages of energy conservation, high defrosting speed and the like, so the hot gas defrosting is most commonly applied in large and medium-sized refrigeration devices.
In the existing hot gas defrosting technology, high-temperature and high-pressure refrigerant steam is led out from an exhaust of a compressor of a refrigeration system or an air outlet of an oil-gas separator to an evaporator, and a frost layer on the surface of the evaporator is defrosted. The high-temperature high-pressure gas discharged from the compressor enters the evaporator, and when the evaporator starts to defrost after the last refrigeration, a part of refrigerant liquid remains in the evaporator, and after the high-temperature high-pressure gas and the low-temperature refrigerant liquid are mixed, the phenomena of liquid hammer and liquid explosion may occur.
For example, chinese patent document No. CN111380327A discloses a quick freezer with hot gas defrosting function, and chinese patent document No. CN110793246A discloses a hot gas defrosting system and a hot gas defrosting method, both of which adopt a hot gas defrosting technical scheme, wherein in order to prevent the problems of liquid hammer and liquid explosion which may occur, or compressor liquid impact and overload caused by liquid return of a refrigeration system after defrosting is finished, complicated pressure control and protection measures after defrosting of an evaporator are required, so that a plurality of control valve elements are required, and the cost is high and is complicated.
Disclosure of Invention
The invention aims to provide a refrigeration system and an evaporator circulating defrosting method, which are used for solving the problem of high cost caused by liquid hammer and liquid explosion prevention in the conventional hot gas defrosting scheme.
In order to achieve the above object, the scheme of the invention comprises:
the invention relates to a refrigerating system, which comprises a compressor, a condenser, a liquid storage device and at least two evaporation branches, wherein the compressor and the condenser are sequentially connected; the outlet of the condenser is connected with the inlet of the liquid storage device, and the outlet of the liquid storage device is connected with each evaporator through a throttling mechanism; each evaporator is connected with a gating device of the corresponding evaporation branch, and the gating device is also connected with a compressor port to form a refrigeration cycle; a defrosting port is also formed above the liquid level of the refrigerant liquid in the liquid storage device and is connected with the gating devices of the evaporation branches; the circulating defrosting method of the evaporator is realized through the following steps;
for the evaporation branch working in the refrigeration mode, controlling the gating device to communicate the evaporator and the compressor of the corresponding evaporation branch to enable the refrigerant to complete refrigeration cycle;
and for the evaporation branch working in the defrosting mode, controlling the gating device to communicate the evaporator and the defrosting port of the corresponding evaporation branch, and introducing refrigerant gas at the upper part of refrigerant liquid in the liquid storage device into the evaporator to release heat and defrost.
The invention provides a refrigeration system which comprises a compressor, a condenser, a liquid storage device and a plurality of evaporation branches for realizing refrigeration, wherein the compressor, the condenser and the liquid storage device are sequentially connected.
During refrigeration, high-temperature high-pressure refrigerant steam from the compressor releases heat in the condenser to become low-temperature high-pressure refrigerant liquid, the refrigerant liquid stays in the liquid storage device and is stored, then the refrigerant liquid is led into the evaporation branch, the pressure is reduced after passing through the throttling mechanism, the refrigerant liquid is subjected to heat absorption gasification in the evaporator to become low-pressure refrigerant gas, and then the low-pressure refrigerant gas is sucked into the compressor to perform the next round of refrigeration cycle.
When defrosting is carried out, a defrosting port above the liquid level of the liquid storage device is communicated with the evaporator through the gating device, refrigerant gas is formed above refrigerant liquid stored in the liquid storage device, and the refrigerant gas is slightly higher than the ambient temperature and is introduced into the evaporator to carry out heat release defrosting.
The refrigerating system provided by the invention utilizes the refrigerant gas above the refrigerant liquid in the liquid storage device to defrost, and compared with the high-temperature high-pressure refrigerant gas output by the compressor, the temperature of the refrigerant gas is lower, the temperature difference between the refrigerant gas and a frost layer formed on the evaporator is small, and the probability of liquid hammer and liquid explosion is effectively reduced.
Further, the reservoir outlet is connected to a supply header for distributing refrigerant liquid to each evaporation branch, each evaporation branch being connected to the supply header.
The outlet of the liquid storage device is connected with each evaporation branch through the liquid supply collecting pipe, refrigerant liquid in the liquid storage device is distributed to each evaporation branch through the liquid supply collecting pipe, and therefore part of the evaporation branches in the refrigeration system can be controlled to work in a refrigeration mode, and part of the evaporation branches in a defrosting mode are controlled to work in the defrosting mode and are not affected with each other.
Further, an outlet of the liquid storage device is connected with the liquid supply header through a differential pressure valve; when a certain evaporation branch works in a defrosting mode, starting a differential pressure valve, forming high pressure at the upstream of the differential pressure valve, and forming low pressure at the downstream of the differential pressure valve; the refrigerant gas at the upper part of the refrigerant liquid in the liquid storage device is driven by the pressure difference generated by the pressure difference valve to enter the evaporator from the gating device corresponding to the evaporation branch for defrosting, and the refrigerant liquid formed after defrosting is distributed to enter the evaporation branches of other refrigeration modes through the liquid supply header.
When a certain evaporation branch works in a defrosting mode, in order to ensure that refrigerant gas can smoothly flow into an evaporator, the outlet of the liquid storage device is provided with a pressure difference valve, and the pressure difference valve is connected with a liquid supply header. When a certain evaporation branch works in a defrosting mode, the differential pressure valve works, the differential pressure valve enables the upstream of the liquid accumulator to form high pressure, namely the high pressure of a defrosting port above the liquid accumulator, and the downstream of the differential pressure valve to form low pressure, namely the low pressure is formed in the liquid supply header, so that refrigerant gas above the liquid accumulator is driven by the differential pressure to smoothly enter the evaporator through the gating device.
Furthermore, the evaporation branch comprises a throttling mechanism, an evaporator and a gating device which are sequentially connected, wherein a reverse pipeline is connected in parallel on the throttling mechanism, and a one-way valve in the direction from the evaporator to the liquid supply header is serially arranged in the reverse pipeline.
Each evaporation branch is provided with a throttling mechanism in each evaporation branch, each throttling mechanism is connected with a reverse pipeline in parallel, a one-way valve is arranged in each reverse pipeline, refrigerant gas above the liquid storage device enters the evaporator through a gating device to be defrosted to form refrigerant liquid, the refrigerant liquid with a large supercooling degree formed after the evaporator is defrosted can flow to the liquid supply header through the one-way valve, the refrigerant liquid with a large supercooling degree formed after the evaporator is defrosted returns to the liquid supply header, the refrigerant liquid is redistributed to other evaporation branches working in a refrigeration mode through the liquid supply header to be used for evaporation refrigeration, the refrigerant for defrosting is reused, namely, heat in a refrigerated environment is used for defrosting the evaporator, and the refrigeration efficiency is not reduced in the defrosting process; or the 'cold energy' stored in the frosting of the evaporator is transferred to other evaporators for refrigeration, so that the refrigeration effect in defrosting is improved.
Furthermore, the gating device is a three-way valve, a first port of the three-way valve is connected with the evaporator corresponding to the evaporation branch, a second port of the three-way valve is connected with the inlet of the compressor, and a third port of the three-way valve is connected with the defrosting port; in the refrigeration mode, a first port and a second port of the three-way valve are communicated; and when in the defrosting mode, the first port and the third port of the three-way valve are communicated.
Furthermore, a stop valve is arranged in the evaporation branch.
Still be provided with the stop valve in each evaporation branch road, when certain evaporation branch road breaks down, close this stop valve, make things convenient for the maintenance of this section evaporation branch road.
Further, the defrosting port is connected with a defrosting header, and the defrosting header is connected with the three-way valve in each evaporation branch to distribute refrigerant gas to each evaporation branch working in a defrosting mode.
A defrost header is provided above the accumulator, the defrost header connecting the three-way valves in the respective evaporation legs, refrigerant gas above the refrigerant liquid in the accumulator being distributed by the defrost header to each evaporation leg operating in defrost mode.
Furthermore, the reversing devices of the branches are connected with the compressor through a gas-separation type air suction header, and refrigerant liquid is subjected to gas-liquid separation in the gas-separation type air suction header after being subjected to heat absorption and liquefaction in the evaporation branch and then is introduced into the compressor.
The reversing device is connected through the gas-separating type air suction collecting pipe, and the gas-separating type air suction collecting pipe is used for carrying out gas-liquid separation on the refrigerant liquid, so that the compressor is ensured to suck dry refrigerant gas.
The invention also provides an evaporator circulating defrosting method which comprises the refrigeration system.
Drawings
FIG. 1 is a schematic diagram of the refrigeration operation of the refrigeration system of the present invention;
which comprises the following steps: 01-compressor, 02-oil separator, 03-condenser, 04-liquid reservoir, 05-dry filter, 06-liquid sight glass, 07-electromagnetic differential pressure valve, 08-liquid supply header, 09-cool air header, 10-air suction header, 11/21/31-two-way electromagnetic valve, 12/22/32-throttling mechanism, 13/23/33-one-way valve, 14/24/34-evaporator and 15/25/35-electromagnetic three-way valve;
FIG. 2 is a schematic diagram of the operation of the solenoid three-way valve of the present invention;
fig. 3 is a schematic diagram of the defrost operation of the refrigeration system of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
The embodiment of the system comprises:
in the prior art, a hot gas defrosting technology is used to avoid the phenomenon of liquid hammer and liquid explosion after high-temperature and high-pressure gas and low-temperature refrigerating liquid are mixed, the refrigerant in the evaporator is stopped to be supplied before defrosting is started, then the compressor operates, and the evaporator is connected to an air suction port of the compressor, so that the refrigerant liquid remaining in the evaporator can be pumped away after the compressor operates, and then when defrosting is performed, after the high-temperature and high-pressure gas enters the evaporator, the evaporator does not have low-temperature refrigerant liquid, and the situation of liquid hammer and liquid explosion cannot occur.
However, after the defrosting is completed, the temperature in the evaporator is low, and thus the high-temperature and high-pressure refrigerant is condensed into liquid in the evaporator. The refrigeration system in the prior art mostly adopts a gas compressor when leaving a factory, and for the gas compressor, the refrigerant liquid condensed in the evaporator can greatly reduce the refrigeration effect of the whole system (the air pump is afraid of liquid). Therefore, in order to convert the liquid in the evaporator into gas, a pressure reducing valve is arranged between the evaporator and the compressor, the liquid in the evaporator is slowly changed into gas by the pressure reducing valve, and then the compressor pumps the part of gas. Until the pressure drop in the evaporator is relatively low, it indicates that the amount of liquid in the evaporator is small, at this time, the valves between the evaporator and the compressor can not be fully opened, and before that, the valves are always in the opening state with small flow, and the valves can not be in the opening state with small flow for a long time, so that the whole refrigeration efficiency of the refrigeration system can be reduced, and under the technology, errors can be easily caused by adjusting the opening and closing degree of the valves.
Taking a low-temperature refrigeration house (18 ℃ below zero) with a piston compressor as an example of a refrigeration system, the exhaust temperature of the compressor can reach about 120 ℃ under the working condition of summer, the temperature of an evaporator is about 28 ℃ below zero, and the large temperature difference can cause the fit clearance between a copper pipe and fins of the evaporator to be gradually increased, so that the contact thermal resistance at the position is gradually increased, and the heat exchange performance of the evaporator is influenced.
Large and medium-sized refrigeration systems are usually provided with an accumulator, and under normal conditions, the lower part of the accumulator is refrigerant liquid, and the upper part of the accumulator is refrigerant gas, and the refrigerant gas at the upper part of the accumulator is utilized to defrost an evaporator. In the existing hot gas defrosting technology, if the amount of liquid refrigerant in the evaporator before defrosting is large, overheated refrigerant vapor enters the evaporator, and the liquid refrigerant is rapidly gasified and changes phase, which may cause a liquid hammer phenomenon. The invention utilizes the lower temperature of the refrigerant gas at the upper part of the liquid storage device, the smaller temperature difference between the refrigerant gas and the evaporator, the temperature of the refrigerant gas can just meet the defrosting requirement of the evaporator, and the probability of liquid hammer and liquid explosion is effectively reduced.
Specifically, as shown in fig. 1, in the refrigeration operation of the refrigeration system of the present invention, low-temperature and low-pressure refrigerant vapor is sucked by a compressor 01, the low-temperature and low-pressure refrigerant vapor is compressed by the compressor into high-temperature and high-pressure refrigerant vapor, the high-temperature and high-pressure refrigerant vapor passes through an oil separator 02, the oil separator 02 separates refrigerant and lubricating oil in the high-temperature and high-pressure refrigerant vapor, the lubricating oil sinks to the bottom of the oil separator 02, the separated high-temperature and high-pressure refrigerant vapor enters a condenser 03, the condenser 03 condenses the high-temperature and high-pressure refrigerant vapor into refrigerant liquid, the condensed refrigerant liquid enters an accumulator 04, when the condenser 03 condenses the high-temperature and high-pressure refrigerant vapor into refrigerant liquid, not all the high-temperature and high-pressure refrigerant vapor can be condensed into refrigerant liquid, and a part of the high-temperature and high-pressure refrigerant vapor can be cooled after passing through the condenser 03, refrigerant gas that is formed to be higher in temperature than the ambient temperature but much lower in temperature than the high-temperature and high-pressure refrigerant vapor is stored in the upper portion of the accumulator 04. After entering the liquid storage device 04, the refrigerant liquid passes through the drying filter 05, the liquid observation mirror 06, the electromagnetic differential pressure valve 07 and the liquid supply header 08, and is distributed to the liquid supply branch corresponding to each evaporator after passing through the liquid supply header 08.
In large and medium-sized refrigeration systems, there is usually more than one evaporator, and when any one evaporator in the refrigeration system is in a non-defrosting state, the electromagnetic differential pressure valve 07 does not work or is in a power-off state, and at this time, the electromagnetic differential pressure valve 07 has no pressure reduction function. When any evaporator is frosted, the electromagnetic differential pressure valve 07 works or is in an electrified state, and at the moment, the inlet and the outlet of the electromagnetic differential pressure valve 07 generate differential pressure so that condensed refrigerant liquid in the defrosting evaporator smoothly flows back to the liquid supply header 08, namely, when the electromagnetic differential pressure valve 07 works, one end connected with the liquid viewing mirror 06 is the inlet of the electromagnetic differential pressure valve to generate high pressure, and the other end connected with the liquid supply header 08 is the outlet of the electromagnetic differential pressure valve to generate low pressure, so that differential pressure is formed in the whole defrosting pipeline, and the refrigerant liquid flows back to the liquid supply header 08.
Each liquid supply branch connected with the liquid supply header 08 is respectively provided with an electromagnetic three-way valve, taking a branch where the evaporator 14 and the electromagnetic three-way valve 15 are located as an example, as shown in fig. 2, when the evaporator 14 is refrigerated, the electromagnetic three-way valve is powered off, so that the ports a and b of the electromagnetic three-way valve 15 are communicated, and refrigerant enters from the port a and is discharged from the port b; when the evaporator 14 defrosts, the electromagnetic three-way valve is energized, so that the port c and the port a of the electromagnetic three-way valve 15 are communicated, and refrigerant enters from the port c and is discharged from the port a. The three-way solenoid valve 25, the three-way solenoid valve 35, and the three-way solenoid valve 15 are based on the same operation principle.
When the refrigeration system of the invention is used for refrigeration or defrosting, the following method is adopted, namely the evaporator circulation defrosting method of the invention.
Taking the branch where the evaporator 14 is located as an example, when the refrigeration system performs refrigeration, the refrigerant liquid from the liquid supply header 08 passes through the two-way solenoid valve 11 and the throttling mechanism 12 in sequence (the refrigerant cannot pass through the one-way valve because the one-way valve 13 is in reverse cut-off), the refrigerant liquid is throttled and decompressed into a low-temperature and low-pressure gas-liquid two-phase refrigerant in the throttling mechanism 12, the liquid refrigerant flows into the evaporator 14, is gasified and absorbs heat through the evaporator 14 to generate a refrigeration effect, the refrigerant gas flows in and out through the ports a and b of the solenoid three-way valve 15 and then enters the gas-split type air suction header 10, the gas-split air suction header 10 has the function of a gas-liquid separator, the low-temperature and low-pressure refrigerant vapor is sent into the compressor 01, the compressor 01 sucks the low-temperature and low-pressure refrigerant vapor, and the whole air conditioner performs refrigeration work in a circulating mode.
In the case of defrosting of any evaporator in the refrigeration system, the present invention takes the evaporator 14 as an example, and as shown in fig. 3, the refrigerant gas in the upper portion of the accumulator 04 is usually slightly warmer than ambient temperature, much cooler than the temperature of the compressor discharge or the refrigerant exiting the oil separator. In order to distinguish from the conventional method using high-temperature and high-pressure refrigerant vapor ("hot-gas defrosting"), the refrigerant gas at the upper part of the accumulator 04 is called as "cool air", and the corresponding pipeline for collecting the cool air is the cool air header 09. At this time, the electromagnetic differential pressure valve 07 operates to make the upper pressure of the accumulator 04 small and the lower pressure large (i.e. the pressure of the accumulator inlet connected to the condenser and the cold air header is large, and the pressure of the accumulator outlet connected to the drying filter is small), so as to ensure that the cold air header 09 collects the cold air, then the cold air enters the evaporator 14 through the port c and the port a of the electromagnetic three-way valve 15, the cold air enters the evaporator, after entering the evaporator, releases heat to the frost layer on the surface of the evaporator to melt the frost layer, when the cold air defrosts the evaporator, the cold air is condensed into refrigerant liquid with large supercooling degree, the refrigerant liquid enters the liquid supply header 08 through the check valve 13 and the two-way electromagnetic valve 11, and then the refrigerant liquid is distributed to other refrigerating evaporators by the liquid supply header 08.
After the frost layer is completely melted, cool air is continuously supplied to the evaporator 14 for a predetermined time period to evaporate the water on the surface of the evaporator and dry the surface. After the surface of the evaporator is dried, the electromagnetic three-way valve 15 is powered off, the electromagnetic differential pressure valve 07 is powered off, and the evaporator recovers refrigeration. Since the suction manifold 10 also functions as a gas-liquid separator, liquid impact does not occur in the compressor. At the moment when the electromagnetic three-way valve 15 is powered off, the pressure in the air suction header pipe can be increased, but because a large or medium-sized refrigeration system usually adopts a screw compressor or a compressor which is connected in parallel (a scroll compressor, a piston compressor and a screw compressor are adopted), and the screw compressor or the compressor which is connected in parallel has an energy regulating function, the compressor cannot be overloaded.
The invention adopts the refrigerant gas at the upper part of the liquid accumulator to defrost the evaporators, reasonably groups the evaporators of the whole refrigerating system, and carries out circulating defrosting when the load of the condenser is larger, thereby greatly reducing the heat load of the condenser, selecting the condenser with smaller rated heat exchange amount at the time of selecting the type of the condenser and saving the initial investment. The invention can also consume no external energy when the evaporator defrosts, and compared with hot-gas defrosting, the invention uses the refrigerant gas from the liquid accumulator with lower temperature, thus the defrosting has little influence on the temperature of the refrigerating space, namely the temperature fluctuation of the refrigerating space is small. In addition, the invention utilizes the refrigerant gas from the upper part of the liquid accumulator to exchange heat with frost on the evaporator and then change the phase into the supercooled liquid, and then the supercooled liquid enters other evaporators through the liquid supply header to be refrigerated, thereby fully utilizing the part of cold energy and improving the energy efficiency of the whole system. After the high-temperature and high-pressure refrigerant discharged by the compressor reaches the condenser through the oil separator, the refrigerant is condensed, the lubricating oil wrapped in the refrigerant can be condensed into small liquid drops, and the liquid drops of the lubricating oil sink in the liquid storage device under the action of gravity, so that the oil content of the refrigerant in the whole refrigeration or defrosting process is reduced.
The method comprises the following steps:
the invention also provides an evaporator circulation defrosting method which is already described in the system embodiment and is not described herein again.
Claims (9)
1. A refrigerating system comprises a compressor and a condenser which are connected in sequence, and is characterized by also comprising a liquid storage device for storing condensed refrigerant liquid and at least two evaporation branches, wherein each evaporation branch comprises an evaporator and a gating device; the outlet of the condenser is connected with the inlet of the liquid storage device, and the outlet of the liquid storage device is connected with each evaporator through a throttling mechanism; each evaporator is connected with a gating device corresponding to the evaporation branch, and the gating device is also connected with a compressor port to form a refrigeration cycle; a defrosting port is also formed above the liquid level of the refrigerant liquid in the liquid storage device and is connected with the gating devices of the evaporation branches; the circulating defrosting method of the evaporator is realized through the following steps;
for the evaporation branch working in the refrigeration mode, controlling the gating device to communicate the evaporator and the compressor corresponding to the evaporation branch so as to enable the refrigerant to complete the refrigeration cycle;
and for the evaporation branch working in the defrosting mode, controlling the gating device to communicate the evaporator and the defrosting port of the corresponding evaporation branch, and introducing refrigerant gas at the upper part of refrigerant liquid in the liquid storage device into the evaporator to release heat and defrost.
2. A refrigeration system as set forth in claim 1 wherein said accumulator outlet is connected to a liquid supply header for distributing refrigerant liquid to each of the evaporation legs, each evaporation leg being connected to the liquid supply header.
3. The refrigerant system as set forth in claim 2, wherein the accumulator outlet is connected to the supply header by a differential pressure valve; when a certain evaporation branch works in a defrosting mode, starting a differential pressure valve, forming high pressure at the upstream of the differential pressure valve, and forming low pressure at the downstream of the differential pressure valve; the refrigerant gas at the upper part of the refrigerant liquid in the liquid storage device is driven by the pressure difference generated by the pressure difference valve to enter the evaporator from the gating device corresponding to the evaporation branch for defrosting, and the refrigerant liquid formed after defrosting is distributed to enter the evaporation branches of other refrigeration modes through the liquid supply header.
4. The refrigeration system as recited in claim 3 wherein said evaporation branch comprises a throttling mechanism, an evaporator and a gating device connected in series, said throttling mechanism having a reverse conduit connected in parallel, said reverse conduit having a one-way valve in series from said evaporator to said header.
5. The refrigeration system according to claim 4, wherein the gating device is a three-way valve, a first port of the three-way valve is connected with the evaporator corresponding to the evaporation branch, a second port of the three-way valve is connected with the inlet of the compressor, and a third port of the three-way valve is connected with the defrosting port; in the refrigeration mode, a first port and a second port of the three-way valve are communicated; and when in the defrosting mode, the first port and the third port of the three-way valve are communicated.
6. The refrigerant system as set forth in claim 5, wherein a shutoff valve is further disposed in said evaporation branch.
7. The refrigerant system as set forth in claim 6, wherein said defrost port is connected to a defrost header, said defrost header connecting the three-way valve in each evaporation branch for distributing refrigerant gas to each evaporation branch operating in a defrost mode.
8. The refrigeration system as recited in claim 7 wherein the reversing device of each branch is connected to the compressor by a gas-split suction header, and the refrigerant liquid is liquefied by heat absorption in the evaporation branch and then introduced into the compressor after gas-liquid separation in the gas-split suction header.
9. An evaporator cycle defrosting method comprising the refrigeration system according to any one of claims 1 to 8.
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