DK2318782T3 - COOLING CIRCUIT - Google Patents

COOLING CIRCUIT Download PDF

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Publication number
DK2318782T3
DK2318782T3 DK09776929.3T DK09776929T DK2318782T3 DK 2318782 T3 DK2318782 T3 DK 2318782T3 DK 09776929 T DK09776929 T DK 09776929T DK 2318782 T3 DK2318782 T3 DK 2318782T3
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DK
Denmark
Prior art keywords
collecting container
sensor
cooling circuit
pressure
predetermined threshold
Prior art date
Application number
DK09776929.3T
Other languages
Danish (da)
Inventor
Markus Hafkemeyer
Christoph Kren
Oliver Finckh
Tobias H Sienel
Rainer Schrey
Original Assignee
Carrier Corp
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Filing date
Publication date
Application filed by Carrier Corp filed Critical Carrier Corp
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Publication of DK2318782T3 publication Critical patent/DK2318782T3/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • F25B49/027—Condenser control 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
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
    • F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle
    • F25B1/10—Compression machines, plants or systems with non-reversible cycle with multi-stage compression
    • 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
    • F25B2309/00—Gas cycle refrigeration machines
    • F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
    • F25B2309/061—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide with cycle highest pressure above the supercritical pressure
    • 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
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/01—Heaters
    • 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
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/04—Refrigeration circuit bypassing means
    • 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
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/22—Refrigeration systems for supermarkets
    • 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
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/23—Separators
    • 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
    • F25B2500/31—Low ambient temperatures
    • 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
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/04—Refrigerant level
    • 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
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2109—Temperatures of a separator

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Devices That Are Associated With Refrigeration Equipment (AREA)
  • Air Conditioning Control Device (AREA)
  • Separation By Low-Temperature Treatments (AREA)
  • Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)

Description

DESCRIPTION
[0001] The invention relates to a refrigeration circuit and to a method of transcritical operation of a refrigeration circuit.
[0002] Current CO2 refrigeration circuits employ a two-stage expansion where the refrigerant is relieved from a high pressure level to a medium pressure level by a first stage expansion device, and where the expansion devices upstream of the evaporators further expand the refrigerant to a suction pressure level.
[0003] WO 2006/015629 A1 discloses a refrigeration circuit for circulating a refrigerant in a predetermined flow direction, comprising in flow direction a heat rejecting heat exchanger, an intermediate throttle valve, a receiver, an evaporator throttle valve, an evaporator, a compressor, and a flash gas tapping line connected to the receiver, wherein the flash gas tapping line is further connected to the compressor.
[0004] When operated at ambient temperatures of less than 10° C such refrigeration circuits often face the problem of maintaining the medium pressure at a sufficiently high level in order that the evaporators downstream can provide adequate cooling performance. Sometimes the medium pressure collapses, and no refrigerant flow gets to the evaporators in the supermarket which can cause substantial damage to the goods to be sold, since they are no more kept in the necessary temperature range.
[0005] Accordingly, it would be beneficial to provide a refrigeration circuit and a method for transcritical operation of a refrigeration circuit that enable a reliable and sufficient cooling performance even with low ambient temperatures.
[0006] The invention includes a refrigeration circuit having a mono- or multi-component refrigerant, especially CO2, circulating therein, said refrigeration circuit enabling an transcritical operation, said refrigeration circuit comprising, in the direction of refrigerant flow, a compressor unit, a condenser/gascooler, a high pressure control valve, a collecting container, and at least one evaporator having an expansion device connected upstream thereof, wherein a flashgas line having a medium pressure control valve arranged therein is provided between an upper portion of the collecting container and the suction line leading to the compressor unit, wherein a temperature, pressure or liquid level sensor is provided in or at the collecting container, wherein a collecting container heating unit arranged in the collecting container, and wherein a control unit is provided said control unit being configured to effect heating operation of the collecting container heating unit when the temperature or pressure in the collecting container sensed by the sensor falls below a predetermined threshold or the liquid level in the collecting container sensed by the sensor exceeds a predetermined threshold, such that the medium pressure is prevented from decreasing.
[0007] The invention further includes a refrigeration circuit having a mono- or multi-component DK/EP 2318782 T3 refrigerant, especially CO2, circulating therein, said refrigeration circuit enabling an transcritical operation, said refrigeration circuit comprising, in the direction of refrigerant flow, a compressor unit, a condenser/gascooler with at least one fan leading air over its surface, a high pressure control valve, a collecting container, and at least one evaporator having an expansion device connected upstream thereof, wherein a flashgas line having a medium pressure control valve arranged therein is provided between an upper portion of the collecting container and the suction line leading to the compressor unit, wherein a temperature, pressure or liquid level sensor is provided in or at the collecting container, and wherein a control unit is provided said control unit being configured to lower the performance of the fan(s) when the temperature or pressure in the collecting container sensed by the sensor falls below a predetermined threshold or the liquid level in the collecting container sensed by the sensor exceeds a predetermined threshold, such that the medium pressure is prevented from decreasing.
[0008] Exemplary embodiments of the invention also include a method for transcritical operation of a refrigeration circuit according to an exemplary embodiment of the invention, in which the collecting container heating unit is operated accordingly when the temperature or pressure in the collecting container sensed by the sensor falls below a predetermined threshold or the liquid level in the collecting container sensed by the sensor exceeds a predetermined threshold, such that the medium pressure is prevented from decreasing, [0009] Exemplary embodiments of the invention further include a method for transcritical operation of a refrigeration circuit, in which the medium pressure holding valve is switched accordingly when the temperature or pressure in the collecting container sensed by the sensor falls below a predetermined threshold or the liquid level in the collecting container sensed by the sensor exceeds a predetermined threshold, such that the medium pressure is prevented from decreasing.
[0010] Exemplary embodiments of the invention also include a method for transcritical operation of a refrigeration circuit according to an exemplary embodiment of the invention, in which the performance of the fan(s) is lowered when the temperature or pressure in the collecting container sensed by the sensor falls below a predetermined threshold or the liquid level in the collecting container sensed by the sensor exceeds a predetermined threshold, such that the medium pressure is prevented from decreasing.
[0011] Embodiments of the invention are described in greater detail below with reference to the figures, wherein
Figure 1 shows a schematic view of a first refrigeration circuit which is not an embodiment of the claimed invention;
Figure 2 shows a schematic view of a second refrigeration circuit which is not an embodiment of the claimed invention;
Figure 3 shows a schematic view of a third refrigeration circuit which is not an embodiment of the claimed invention; DK/EP 2318782 T3
Figure 4 shows a schematic view of a fourth refrigeration circuit which is not an embodiment of the claimed invention;
Figure 5 shows a schematic view of a fifth refrigeration circuit which is not an embodiment of the claimed invention;
Figure 6 shows a schematic view of a sixth refrigeration circuit which is not an embodiment of the claimed invention;
Figure 7 shows a schematic view of a seventh refrigeration circuit according to first and second embodiments of the invention; and
Figure 8 shows a schematic view of an eighth refrigeration circuit which is not an embodiment of the claimed invention.
[0012] Figure 1 shows a schematic view of a first refrigeration circuit 2, which is not an embodiment of the claimed invention.
[0013] The first refrigeration circuit 2 and all other refrigeration circuits explained with respect to figures 2-8 below, comprise the following corresponding elements that are designated with like reference numerals. The refrigeration circuits explained below comprise, in the direction of refrigerant flow, a compressor unit 4 having three compressors connected in parallel, a condenser/gas cooler 6 having two fans 8 and respective fan controls 10 for flowing ambient air over its surface, a high pressure control valve 12, a collecting container/receiver 14, where gaseous and liquid refrigerant are separated from each other and collected, and two evaporators 18 and 20 having a respective expansion valve 16, 20 connected upstream thereof.
[0014] The condenser/gas cooler 6 acts as a condenser when the refrigerant circuit is operating in a subcritical mode and as a gas cooler when the refrigerant circuit is operating in a transcritical mode. When the ambient temperatures are lower than 10° Celsius, the gas cooler 6 normally works as a condenser/liquefier.
[0015] The compressors of the compressor unit 4 can also be connected in series.
[0016] A flashgas line 24 having a medium pressure control valve 26 arranged therein connects the gas space, especially a point in the upper portion of the collecting container 14 with the suction line of the compressor unit 4. Further, a sensor 28 is provided in or at the collecting container 14, especially in an upper portion thereof.
[0017] The sensor 28 can be configured as temperature sensor measuring the temperature within the collecting container 14, as pressure sensor sensing the pressure within the collecting container 14, as liquid level sensor sensing the liquid level of liquid refrigerant in the collecting DK/EP 2318782 T3 container 14 or as a combination thereof.
[0018] It is further to be mentioned that the high pressure control valve 12 effects the phase change of the refrigerant and only a small temperature decrease in the order of 10 Celsius.
[0019] As a matter of course the number of compressors of the compressor unit 4, the number of the fans 8 and fan controls 10 and the number of evaporators 18 and 22 is only examplary, and different numbers of such elements can also be provided.
[0020] All refrigeration circuits depicted in figures 1 - 8 and explained with respect to these figures further comprise a control unit that effects the particular medium pressure control operation in case the sensor senses a too low pressure or temperature within the collecting container 14 or a too high level of liquid refrigerant within the collecting container 14. This situation particularly occurs, when the refrigerant flowing from the high pressure control valve 12 into the collecting container 14 is colder than the refrigerant already collected within the collecting container 14. In this case a pressure and temperature decrease within the collecting container 14 can be avoided and an efficient medium pressure control can be provided that guarantees sufficient cooling performance of the evaporators 18 and 22. In a situation when no flash gas is generated and only liquid refrigerant gets into the collecting container 14, the pressure will collapse and the refrigerant circuit will stop operating. This problem is reliably avoided by the refrigeration circuits and the methods for transcritical operation of a refrigerant circuit, according to exemplary embodiments of the invention, as explained below.
[0021] Normal pressure levels of the refrigeration circuits depicted in figures 1 - 8 are as follows: High pressure level between the compressor unit 4 and the high pressure control valve 12: 100 - 125 bar approx., medium pressure level between the high pressure control valve 12 and the expansion valves 16 and 20: 35 - 36 bar, and suction pressure level between the evaporators 18 and 22 and the compressor unit 4: 10-26 bar.
[0022] Reverting now to the first refrigeration circuit 2, this first refrigeration circuit 2 further comprises a bypass line 30 having a medium pressure holding valve 32 arranged therein. This bypass line 30 connects the line between the condenser/gas cooler 6 and the high pressure control valve 12 to the line portion downstream the collecting container 14 at a position between the collecting container 14 and the expansion valves 16 and 20. In other words, the medium pressure holding valve 32, which can be a solenoid valve, is connected in parallel with the high pressure control valve 12 and the collecting container 14.
[0023] If the sensor 28 senses a too low pressure or temperature value within the collecting container 14 or a too high liquid level of the liquid refrigerant within the collecting container 14 it opens the medium pressure holding valve 32 such that liquid refrigerant bypasses the high pressure control valve 12 and the collecting container 14 and flows directly into the line portion downstream of the collecting container 14. Thereby the medium pressure can reliably controlled and it is avoided that refrigerant being colder than the refrigerant collected in the collecting container 14 flows into the collecting container 14. DK/EP 2318782 T3 [0024] Figure 2 shows a schematic view of a second refrigeration circuit 34, which is not an embodiment of the claimed invention.
[0025] The second refrigeration circuit 34 comprises, instead of the bypass line 30 and the medium pressure holding valve 32, a bypass line 38 connecting the line after the high pressure control valve 12 to the line portion downstream the collecting container 14 at a position between the collecting container 14 and the expansion valves 16 and 20, and a medium pressure holding valve 36 being arranged in the line after the branch off point of the bypass line 38 and before the collecting container 14. In other words, a bypass line 38 bypasses the collecting container 14 and the medium pressure holding valve 36 is put in series after the high pressure control valve 12 and after the branch off point of the bypass line 38.
[0026] If the temperature or pressure in the collecting container 14 sensed by the sensor 28 falls below a pre-determined threshold or the liquid level in the collecting container sensed by the sensor 28 exceeds a predetermined threshold, the control unit closes the medium pressure holding valve 36 such that the refrigerant bypasses the collecting container 14 over the bypass line 38. In this way a temperature or pressure decrease in the collecting container 14 can be avoided and the medium pressure within the collecting container can be kept constant.
[0027] In particular the bypass pipe needs to be located above the collecting container 14.
[0028] Figure 3 shows a schematic view of a third refrigeration circuit 40, which is not an embodiment of the claimed invention.
[0029] Compared to the second refrigeration circuit 34, the third refrigeration circuit 40 lacks the medium pressure holding valve 36 and has a medium pressure holding valve 42 arranged in the bypass line 38 instead. In other words, the medium pressure holding valve 42 is incorporated to bypass the collecting container 42.
[0030] When the temperature or pressure in the collecting container 14 gets too low or the liquid level gets too high, the control unit opens the medium pressure holding valve 42 and refrigerant bypasses the collecting container 14. By such operation a temperature or pressure decrease in the collecting container 14 can be reliably avoided. Furthermore a gas phase within the collecting container 14 can be maintained.
[0031] In particular the bypass line 38 is placed below the collecting container 14.
[0032] Figure 4 shows a schematic view of a fourth refrigeration circuit 44, which is not an embodiment of the claimed invention.
[0033] Compared to the second refrigeration circuit 34, the medium pressure holding valve 36 upstream of the collecting container 14 is omitted, and a medium pressure holding valve 46 is provided in the line portion downstream of the collecting container 14 at a position after the DK/EP 2318782 T3 collecting container 14 and before the refeed point of the bypass line 38.
[0034] When the temperature or pressure in the collecting container 14 gets too low or the liquid level gets too high, the control unit closes the medium pressure holding valve, and liquid refrigerant bypasses the receiver 14 via the bypass line 38.
[0035] To ensure proper functionality during bypass and normal operation, a phase change separator can be placed at the branch off point of the bypass line 38 before the collecting container 14.
[0036] Figure 5 shows a schematic view of a fifth refrigeration circuit 48, which is not an embodiment of the claimed invention.
[0037] Instead of bypassing the collecting container 14 as realized by the refrigeration circuits 2, 34, 40 and 44 depicted in figures 1 - 4, the fifth refrigeration circuit 48 provides a bypass line 50 in parallel to the condenser/gas cooler 6. In such bypass line 50, a medium pressure holding valve 52 is arranged.
[0038] When the temperature or pressure in the collecting container 14 gets too low or the liquid level gets too high, the control unit opens the medium pressure holding valve 52 such that hot pressurized refrigerant bypasses the condenser/gas cooler 6 and mixes with the refrigerant having passed the condenser/gas cooler 6 at or after the refeed point of the bypass line 50.
[0039] Thereby it is ensured that hot gaseous refrigerant reaches the collecting container 14, and therefore the temperature and pressure in the collecting container 14 can be increased or at least kept constant and a sufficient amount of gaseous refrigerant in the collecting container 14 can be provided.
[0040] Figure 6 shows a schematic view of a sixth refrigeration circuit 54, which is not an embodiment of the claimed invention.
[0041] The sixth refrigeration circuit 54 comprises a bypass line 56 connecting the pressure line after the compressor unit 4 with the flash gas line 24 at a position close to the collecting container 14 and before the medium pressure control valve 26.
[0042] When the temperature or pressure within the collecting container 14 gets too low or the liquid level gets too high, the control unit actuates or opens the medium pressure holding valve 58 such that hot gaseous refrigerant flows from the pressure line into the gas space of the collecting container 14. Thereby, a temperature or pressure decrease in the collecting container 14 can be avoided, and a sufficient amount of gaseous refrigerant within the collecting container 14 can be provided.
[0043] Figure 7 shows a schematic view of a seventh refrigeration circuit 60 representing first DK/EP 2318782 T3 and second embodiments of the invention.
[0044] Instead of providing bypass lines and an additional medium pressure holding valve, the seventh refrigeration circuit 60 provides two medium pressure control embodiments, that can be employed independently from each other.
[0045] As a first embodiment, the sixth refrigeration circuit 60 comprises a collecting container heating unit 62, which in case the temperature or pressure within the collecting container 14 gets too low or the liquid level gets too high, is switched on by the control unit and heats the refrigerant within the collecting container 14. In particular at high liquid level boiling of the refrigerant will supply sufficient refrigerant gas formation. Hence, a pressure or temperature decrease within the collecting container 14 can be avoided, and a sufficient amount of gaseous refrigerant in the collecting container 14 can be provided.
[0046] According to a second, alternative embodiment, the control unit lowers the performance of at least one of the fans 8, when the temperature or pressure in the collecting container 14 gets too low or the liquid level gets too high. By such lowering of the fan performance, the efficiency of the condenser/gas cooler 6 is lowered such that the heat extraction within the condenser/gas cooler is reduced which will supply sufficient refrigerant in gaseous form to the collecting container 14. Such lowered performance of the condenser/gas cooler 6 can either be achieved by switching off fans or stage-wise reduction of the fans running, or a variable speed drive can be provided or integrated in the control unit that continuously lowers the performance of the fans 8.
[0047] Figure 8 shows a schematic view of an eighth refrigeration circuit 64, which is not an embodiment of the claimed invention.
[0048] The eighth refrigeration circuit 64 comprises all medium pressure control units of the first to seventh refrigeration circuits 2, 34, 40, 44, 48, 54 and 60, namely the collecting container bypass line 30 and the medium pressure holding valve 32, the collecting container bypass line 38 and the medium pressure holding valves 36, 42 and 46, the condenser/gas cooler bypass line 50 and the medium pressure holding valve 52, the bypass line 56 and the medium pressure holding valve 58, the collecting container heating unit 62 and the fan performance control.
[0049] In the eighth refrigeration circuit 64 one, two or more or even all of those medium pressure control units can be employed as appropriate.
[0050] It is explicitly disclosed therein, that the medium pressure control units described with respect to figures 1 - 7 can be combined in any fashion, and the right to direct claims on any of such combination of measurement units is explicitly reserved.
[0051] In all refrigeration circuits, as described herein, at least one of a pressure sensor, a temperature sensor and a liquid level sensor is provided in or at the collecting container 14, DK/EP 2318782 T3 and the sensed values are transmitted to and used by the control unit which in turn actuates the respective medium pressure holding valves 32, 36, 42, 46, 52 and 58, and/or the collecting container heating unit 62 and/or the fan(s) 8.
[0052] In general, the refrigerant circuits of the invention, as described herein, can be operated with any conventional refrigerant. Particularly, CO2 can be circulated within the refrigerant circuits. More particularly, CO2 can be used as refrigerant, and the refrigeration circuit can be operated in a transcritical mode.
[0053] According to exemplary embodiments of the invention, as described herein, a reliable and energy efficient medium pressure control of transcritical refrigeration systems, especially transcritical CO2 refrigeration systems within the collecting container in the event of low ambient temperatures is attained. All exemplary embodiments of the invention, as described herein, have one more benefit: they save on energy consumption.
[0054] By the high pressure control valve 12 which acts as a first stage expansion device and reduces the pressure of the cooled refrigerant before entering the refrigerant collecting container 14 to the medium pressure level high pressure refrigerant can be avoided from entering the supermarket. The liquid refrigerant from the collecting container 14 is sent to the evaporators 18, 22 in the supermarket at the medium pressure level to be used in the individual cooling cabinets. The vapor from the collecting container 14 is expanded to the suction pressure return line by the medium pressure control valve 26.
[0055] By the refrigerant circuits according to exemplary embodiments of the invention, as described herein, a reliable transcritical operation at ambient temperatures of less than 10° Celsius can be attained. Problems as occurring in other refrigeration circuits regarding a medium pressure decrease due to lack of vapor at the high pressure control valve 12 can reliable avoided and a sufficient flow of refrigerant at an appropriate pressure to the cabinets in the supermarket is ensured.
[0056] Under normal conditions it suffices that the medium pressure control units, as described above, are operated for a comparatively short time frame of a few seconds in order to avoid a temperature or pressure decrease within the collecting container 14 and to ensure that enough gaseous refrigerant is present within the collecting container 14. For this purpose the medium pressure holding valves 32, 36, 42, 46, 52, and 58 can be configured as solenoid valves.
[0057] In the claims the features of the refrigeration circuit are defined in detail for the refrigeration circuit. As a matter of course, such features can also be present, as corresponding method steps for the respective methods for transcritical operation of a refrigeration circuit, and for such method claims the same advantages apply as for the respective refrigeration circuit.
[0058] While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition many modifications may be made to adopt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention include all embodiments falling within the scope of the claims.
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.
Patent documents cited in the description • W02006015629A1 [00031

Claims (7)

1. Kølekredsløb (60) med et mono- eller multikomponentkølemiddel, især CO2, cirkulerende deri, hvilket kølekredsløb (54) muliggør transkritisk drift, hvilket kølekredsløb (54) i retning af kølemiddelstrømmen omfatter en kompressorenhed (4), en kondensa-tor/gaskøler (6), en højtrykreguleringsventil (12), en opsamlingsbeholder (14) og mindst én fordamper (18, 22) med en ekspansionsanordning (16, 20) forbundet opstrøms deraf, hvor en flashgasledning (24) med en mellemtrykreguleringsventil (26) anbragt deri er tilvejebragt mellem en øvre del af opsamlingsbeholderen (14) og sugeledningen, der fører til kompressorenheden (4), idet en temperatur-, tryk- eller væskeniveausensor (28) er tilvejebragt i eller ved opsamlingsbeholderen (14), kendetegnet ved, at en opsamlingsbeholdervarmeenhed (62) er anbragt i opsamlingsbeholderen (14), og en styreenhed er tilvejebragt, hvilken styreenhed er konfigureret til at bevirke varmedrift af opsamlingsbeholdervarmeenhed (62), når temperaturen eller trykket i opsamlingsbeholderen (14) registreret af sensoren (28) falder under en forudbestemt tærskel eller væskeniveauet i opsamlingsbeholderen (14) registreret af sensoren (28) overstiger en forudbestemt tærskel, således at mellemtrykket forhindres i at falde.A cooling circuit (60) with a mono- or multicomponent refrigerant, in particular CO2, circulating therein, which cooling circuit (54) enables transcritical operation, which cooling circuit (54) in the direction of the refrigerant stream comprises a compressor unit (4), a condenser / gas cooler (6), a high pressure control valve (12), a collection vessel (14) and at least one evaporator (18, 22) with an expansion device (16, 20) connected upstream thereof, a flash gas line (24) with an intermediate pressure control valve (26) disposed therein is provided between an upper part of the collecting vessel (14) and the suction line leading to the compressor unit (4), a temperature, pressure or liquid level sensor (28) being provided in or at the collecting vessel (14), characterized in that a collecting vessel heating unit (62) is disposed in the collection container (14) and a control unit is provided which is configured to effect heat operation of the collection container heating unit (62) when temperature the impurity or pressure in the collecting vessel (14) detected by the sensor (28) falls below a predetermined threshold or the liquid level in the collecting vessel (14) detected by the sensor (28) exceeds a predetermined threshold so that the intermediate pressure is prevented from falling. 2. Kølekredsløb (60) med et mono- eller multikomponentkølemiddel, især CO2, cirkulerende deri, hvilket kølekredsløb (54) muliggør transkritisk drift, hvilket kølekredsløb (54) i retning af kølemiddelstrømmen omfatter en kompressorenhed (4), en kondensa-tor/gaskøler (6) med mindst én ventilator (8), der fører luft over dens overflade, en højtrykreguleringsventil (12), en opsamlingsbeholder (14) og mindst én fordamper (18, 22) med en ekspansionsanordning (16, 20) forbundet opstrøms deraf, hvor en flashgasledning (24) med en mellemtrykreguleringsventil (26) anbragt deri er tilvejebragt mellem en øvre del af opsamlingsbeholderen (14) og sugeledningen, der fører til kompressorenheden (4), idet en temperatur-, tryk- eller væskeniveausensor (28) er tilvejebragt i eller ved opsamlingsbeholderen (14), kendetegnet ved, at en styreenhed (10) er tilvejebragt, hvilken styreenhed (10) er konfigureret til at sænke ydeevnen af ventilatoren eller ventilatorerne (8), når temperaturen eller trykket i opsamlingsbeholderen (14) registreret af sensoren (28) falder under en forudbestemt tærskel eller væskeniveauet i opsamlingsbeholderen (14) registreret af sensoren (28) overstiger en forudbestemt tærskel, således at mellemtrykket forhindres i at falde.2. A cooling circuit (60) with a mono- or multicomponent refrigerant, in particular CO2, circulating therein, which cooling circuit (54) enables transcritical operation, which cooling circuit (54) in the direction of the refrigerant flow comprises a compressor unit (4), a condenser / gas cooler (6) having at least one fan (8) conducting air above its surface, a high pressure control valve (12), a collection vessel (14) and at least one evaporator (18, 22) connected to an expansion device (16, 20) upstream thereof, wherein a flash gas line (24) with an intermediate pressure control valve (26) disposed therein is provided between an upper portion of the collection vessel (14) and the suction line leading to the compressor unit (4), providing a temperature, pressure or liquid level sensor (28) in or at the collection vessel (14), characterized in that a control unit (10) is provided, which control unit (10) is configured to lower the performance of the fan or fans (8) when temperature one or the pressure in the collecting vessel (14) detected by the sensor (28) falls below a predetermined threshold or the liquid level in the collecting vessel (14) detected by the sensor (28) exceeds a predetermined threshold so that the intermediate pressure is prevented from falling. 3. Kølekredsløb (60) ifølge krav 2, hvor styreenheden (10) omfatter en variabel hastighedsdrivkraft til ventilatoren eller ventilatorerne (8).A cooling circuit (60) according to claim 2, wherein the control unit (10) comprises a variable speed driving force for the fan or fans (8). 4. Kølekredsløb (60) ifølge et hvilket som helst af kravene 1 til 3, hvor kompressorenheden (4) omfatter et sæt af kompressorer.A cooling circuit (60) according to any one of claims 1 to 3, wherein the compressor unit (4) comprises a set of compressors. 5. Kølekredsløb (60) ifølge et hvilket som helst af kravene 1 til 4, hvor mindst to fordampere (18, 22) med en tilsvarende ekspansionsanordning (16, 20) forbundet opstrøms deraf er forbundet parallelt.A cooling circuit (60) according to any one of claims 1 to 4, wherein at least two evaporators (18, 22) with a corresponding expansion device (16, 20) connected upstream thereof are connected in parallel. 6. Fremgangsmåde til transkritisk drift af et kølekredsløb ifølge krav 1, hvori opsam-lingsbeholdervarmeenheden (62) drives i overensstemmelse hermed, når temperaturen eller trykket i opsamlingsbeholderen (14) registreret af sensoren (28) falder under en forudbestemt tærskel eller væskeniveauet i opsamlingsbeholderen (14) registreret af sensoren (28) overstiger en forudbestemt tærskel, således at mellemtrykket forhindres i at falde.A method for transcritically operating a cooling circuit according to claim 1, wherein the collection vessel heating unit (62) is operated accordingly when the temperature or pressure in the collecting vessel (14) detected by the sensor (28) falls below a predetermined threshold or the liquid level in the collecting vessel ( 14) detected by the sensor (28) exceeds a predetermined threshold so that the intermediate pressure is prevented from falling. 7. Fremgangsmåde til transkritisk drift af et kølekredsløb ifølge krav 2 eller 3, hvori ydeevnen af ventilatoren eller ventilatorerne (8) sænkes, når temperaturen eller trykket i opsamlingsbeholderen (14) registreret af sensoren (28) falder under en forudbestemt tærskel eller væskeniveauet i opsamlingsbeholderen (14) registreret af sensoren (28) overstiger en forudbestemt tærskel, således at mellemtrykket forhindres i at falde.A method of transcritically operating a cooling circuit according to claim 2 or 3, wherein the performance of the fan (s) (8) is lowered when the temperature or pressure in the collecting container (14) detected by the sensor (28) falls below a predetermined threshold or the liquid level in the collecting container. (14) detected by the sensor (28) exceeds a predetermined threshold so that the intermediate pressure is prevented from falling.
DK09776929.3T 2008-07-07 2009-07-02 COOLING CIRCUIT DK2318782T3 (en)

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