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
  • F25B31/00—Compressor arrangements
  • F25B31/002—Lubrication
  • F25B31/004—Lubrication oil recirculating 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
  • 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
  • F25B2400/07—Details of compressors or related parts
  • F25B2400/075—Details of compressors or related parts with parallel compressors
• • 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
  • F25B2400/13—Economisers
• • 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
  • F25B2500/16—Lubrication
• • 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

Definitions

• a conventional refrigerant circuit comprises a compressor unit, comprising one or a plurality of individual com- pressors, a heat rejecting heat exchanger, an expansion device and an evaporator in flow direction serially connected with each other.
• a two-stage refrigerant circuit comprises two refrigerant circuits working at different temperature levels and connected with each other. In a so called cascade arrangement the two refrigerant circuits are fluidly disconnected from each other and only in a heat exchange relationship connected with each other. In a booster arrangement, the two different level refrigerant circuits are fluidly connected with each other with the outlet of the lower compressor unit being typically at the same pressure level as the inlet of the higher pressure refrigerant circuit.
• a lubricant typically oil
• a lubricant is admixed to the refrigerant in a predetermined amount.
• approximately 2 % of the refrigerant is lubricant and oil, respectively, while the remaining approximately 98 % are the actual refrigerant.
• an oil separator is typically provided in the high pressure line leaving the compressor unit and an oil level regulator is provided for the compressor unit in order to inject lubricant and oil, respectively, into a respective compressor of the compressor unit once the oil level therein is below a predetermined minimum oil level.
• Exemplary embodiments of the invention include a refrigerant circuit comprising a low pressure compressor unit having a low pressure refrigerant outlet in a low pressure sub-circuit and a higher pressure compressor unit having a higher pressure refrigerant inlet in a higher pressure sub-circuit, wherein the low pressure refrigerant outlet and the higher pressure refrigerant inlet are fluidly con- nected with each other, further comprising an oil reservoir connected by a low pressure oil inlet conduit to the low pressure sub-circuit for receiving oil there from and connected via a non-return valve to the higher pressure sub-circuit.
• lubricant and oil are exchangeable, i.e. the term oil is not restricted to oil in its narrow meaning but extends to lubricants as a whole.
• the respective compressor units may each comprise a single or a plurality of individual compressors.
• An other exemplary embodiment of the invention includes a method for managing oil in a refrigerant circuit comprising a low pressure compressor unit having a low pressure refrigerant outlet in a low pressure sub-circuit and a higher pressure compressor unit having a higher pressure refrigerant inlet in a higher pressure sub-circuit, wherein the low pressure refrigerant outlet and the higher pressure refrigerant inlet are fluidly connected with each other, comprising the step of collecting excess oil from the low pressure sub-circuit in an oil reservoir and pressurizing the oil in the oil reservoir for transferring oil into the higher pressure sub-circuit.
• Fig. 1 shows a refrigerant circuit in accordance with one embodiment of the present invention
• Fig. 2 shows part of a refrigerant circuit in accordance with an other embodiment of the present invention
• Fig. 3 shows an other embodiment
• Fig. 4 shows an other embodiment.
• Fig. 1 shows a refrigerant circuit 2 comprising a low pressure sub-circuit 4 and a higher pressure sub-circuit 6.
• the higher pressure sub-circuit 6 comprises a higher pressure compressor unit 8 having a number of individual compressors 10, at least some thereof having a common higher pressure refrigerant inlet 12.
• a higher pressure refrigerant outlet 14 connects compressor unit 18 via a high pressure refrigerant line 16 to a heat rejecting heat exchanger 18 which in case of a conventional refrigerant is typically termed a condenser and in case of a transcritical refrigerant is typically termed a gas cooler. While the present invention is applicable with conventional refrigerants and transcritical refrigerants, a transcritical refrigerant circuit embodying the present invention is pre- ferred. Carbondioxide is a preferred transcritical refrigerant.
• Line 20 connects the heat rejecting heat exchanger 18 with a receiver 22.
• Receiver outlet 24 is connected via an expansion means 26 to an evaporator 28.
• Line 30 connects the output 32 of the evaporator 28 with the medium pressure line 34 which further connects to the higher pressure refrigerant inlet 12.
• An inter cooler circuit 36 serves for sub cooling a refrigerant leaving the receiver 22, as known in the art.
• a branch-off line 45 can be provided connecting a refrigerant line portion at a position before the expansion means 26 with the line 30 at a position before the low pressure expansion device 44, especially at a position between the branching off medium pressure line 34 and the low pressure expansion device 44.
• Low pressure sub-circuit 4 similarly comprises a low pressure compressor unit 38 having a plurality of individual compressors 40 and a common low pressure refrigerant outlet 42 which, in this embodiment, is identical to the medium pressure line 34 and the higher pressure refrigerant inlet 12, but is at least fluidly connected to the higher pressure refrigerant inlet 12.
• a low pressure expansion device 44 and a low pressure evaporator 46 close the low pressure sub-circuit 4 to the low pressure refrigerant inlet 48.
• refrigerant circuits 2 comprising a transcritical refrigerant and particularly carbondioxide.
• This type of refrigerant circuit is adapted for use in a refrigeration apparatus, but the present invention can be used with other refrigerant apparatus, like air conditioning apparatus, etc..
• the low pressure expansion device 44 and evaporator 46 respectively provide the so-called deep temperature cooling, i.e. the cooling of frozen goods in a temperature range of approximately minus 20 to minus 25 0 C within the goods compartment.
• the higher pressure expansion device 26 and evaporator 28 provide the so-called normal temperature cooling for conventional non-frozen goods in a temperature range of around 0 to plus 5 0 C within the goods compartment.
• the temperatures and the pressures of the refrigerant in the system are approximately 10 to 12 bar and minus 40 to minus 35 0 C in the low pressure refrigerant inlet line, approximately 30,5 bar and minus 5 0 C at the low pressure refrigerant outlet 42 and depending on the ambient temperature of the heat rejecting heat exchanger 18 between approximately 80 to 90 bar and approximately 40 0 C in summer operational mode and 45 bar and plus 10 0 C in winter operational mode.
• a higher pressure oil system 50 connects the oil sumps of the compressors 10 with each other in order to provide an equal oil level within the compressors.
• a similar compensation conduit 52 connects the individual compressors 40 of the low pressure compressor unit 38. This compensation conduit 52 is further connected via low pressure oil inlet conduit 54 to an oil reservoir 56.
• a low pres- sure shut-off valve 58 is arranged in the oil inlet conduit 54.
• Oil reservoir 56 is connected by means of oil discharge conduit 60 to the higher pressure sub-circuit 6 and preferably to the higher pressure refrigerant inlet 12.
• the oil discharge conduit 60 comprises an oil discharge valve 62 which preferably is a non-return valve 62, but may also be a shut-off valve.
• a pressure re- lease means 64 is connected to the oil reservoir 56.
• the pressure release means 64 comprises a release conduit 66 connecting the oil reservoir 56 with a low pressure section line 48 and comprises a release valve 68.
• Oil reservoir 56 can be fluidly connected to the oil sump of the low pressure compressor unit 38 and particularly to the individual oil sumps of the compressors 40 so that oil level in the oil sump(s) and the oil reservoir 56 are always flush, if the low pressure discharge valve 58 is in its open state.
• a tapping means (not shown) can be provided for each individual compressor 40 or the whole low pressure compressor unit 38 for tapping just the excess oil from the low pressure compressor unit 38. In both cases excess oil is collected in the oil reservoir 56.
• the low pressure discharge valve 58 is closed and the pressure in the oil reservoir 56 is increased, for example by allowing heating of the oil reservoir 56 and the refrigerant and oil therein by means of ambient conditions.
• the oil reservoir 56 will be in a machine room at a temperature of roughly 20 0 C, while the temperature of the oil and the refrigerant in the oil reservoir 56 will be much lower, dependent on the fluid exchange with the low pressure compressor unit 38.
• the pressure within the oil reservoir 56 will substantially increase and will particularly be above the pressure of roughly 30 bar at the higher pressure refrigerant inlet 12 and once the oil discharge valve 62 opens, the oil can be transferred due to the pressure difference to the higher pressure refrigerant in the line 12.
• the oil discharge valve 62 is a non-return valve, which opens for example if the pressure difference is approximately 0.07 bar, it will automatically open once the pressure in the oil reservoir 56 exceeds the pressure of the higher pressure refrigerant inlet 12.
• the oil discharge valve 62 is a shut-off valve, it can actively be opened and closed for transferring the oil.
• the oil discharge valve 62 closes automatic- ally or will be actively closed and the overpressure of the oil reservoir 56 is discharged to the release valve 68 to the low pressure suction line 48. Once the pressure in the low pressure suction line 48 and the oil reservoir 56 is balanced, the low pressure discharge valve 58 can be opened again in order to allow the collection of excess oil in the oil reservoir 56.
• Sensor means can be provided for detecting whether sufficient excess oil has been collected in the oil reservoir 56 and a control (not shown) can initiate the oil transportation as previously described. It is also possible to provide a timer which after a pre-determined time has elapsed, starts a corres- ponding oil transfer operation. It is within the average skill of the skilled person in the field to provide the necessary sensors, control, etc. for implementing either of the described oil transfer modes.
• the oil discharge valve 62 is closed again and ambient air around the oil reservoir 56 may heat up the refri- gerant and oil within the oil reservoir 56. Already a slight temperature increase will be sufficient to provide a sufficient pressure difference between the oil reservoir and the higher pressure refrigerant inlet line 12 for transferring the oil thereto.
• Fig. 2 discloses an other alternative for generating the necessary pressure difference in the oil reservoir 56 by means of a heater 70 which can be an autonomous heater 70, which is for example electrically powered. It is also possible to direct any hot refrigerant from any other part of the refrigerant circuit through heating lines thus serving as heater 70.
• the embodiment of Fig. 2 corresponds to that of Fig. 1.
• the oil transfer operation corresponds more or less to that of the embodiment of Fig. 1 with the exception that instead of allowing heating up of the oil and refrigerant in the reservoir 56 the heater 70 will be turned on once the low pressure discharge valve 58 has been closed. Again, the oil discharge valve 62 will automatically opened or actively opened so that the pressure difference can drive the oil through the oil discharge line 60 to the higher pressure sub-circuit 6 and preferably the higher pressure refrigerant inlet of the higher pressure compressor unit 8.
• Fig. 3 which is again very similar to that of Fig. 1 and 2, high pressure refrigerant from receiver 22 can be used for pressurizing the oil reservoir 56.
• a pressurizing line 72 connects receiver 22 via pressurizing valve 74 with the oil reservoir 56.
• the oil transfer operation with the embodiment of fig. 3 is again very similar to that of fig. 1 and 2, respectively.
• the pressurizing valve 74 is opened and allows inflow of high pressure refrigerant having a pressure of approximately 40 bar into the oil reservoir 56.
• the discharge valve 62 can open automatically or can actively be opened so that oil is transferred to the higher pressure sub-circuit 6.
• the embodiment of fig. 4 is very similar to the embodiment of fig. 3 but allows to transfer oil from the higher pressure sub-circuit 6 to the low pressure sub-circuit 4 by means of oil transfer conduit 76 and oil transfer valve 78.
• the oil transfer conduit 76 is connected to the higher pressure oil compensation line 8 which connects individual pressures 10 of the higher pressure compressor unit 8 or an individual oil sump of at least one compressor 10.
• a tapping means (not shown) can be provided for tapping just excess oil to the oil transfer conduit 76.
• the conventional oil transfer operation transferring oil from the low pressure sub-circuit 4 to the higher pressure sub-circuit 8 is conventional as disclosed with respect to sub-circuit 4.
• the oil transfer in the opposite direction can for example be performed once the oil discharge valve 62 was closed.
• oil transfer valve 78 If the oil transfer valve 78 is subsequently opened, excess oil from the higher pressure compressor unit 8 may flow, for example due to difference in pressure to the oil reservoir 56. Subsequently, the oil transfer valve 78 will be closed and once the low pressure discharge valve 58 will be opened after releasing the surplus pressure through the release valve 68, normal operation is resumed.
• this low pressure discharge valve 58 can be closed and the oil transfer valve 78 can be opened, so that pressure difference with drive excess oil from the higher pressure sub-circuit to the oil reservoir 56.
• the individual approaches as shown above for increasing the pressure in the oil reservoir 56 for transferring oil to the higher pressure sub-circuit can be used various combinations with each other. It is also possible to use the additional oil transfer conduit 76 and oil transfer valve 78 with any of the above embodiments of Fig. 1 to 3. With the exception of the above-mentioned automatic non-return valve, the actively controlled valves can be solenoid valves, etc..

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Mechanical Engineering (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Compressor (AREA)
• Compressors, Vaccum Pumps And Other Relevant Systems (AREA)
• Organic Insulating Materials (AREA)

Priority Applications (8)

Applications Claiming Priority (1)

Publications (1)

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ID=39166345

Family Applications (1)

Country Status (8)

Cited By (6)

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Citations (6)

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• 2007
  • 2007-09-28 US US12/680,483 patent/US20100251736A1/en not_active Abandoned
  • 2007-09-28 WO PCT/EP2007/008485 patent/WO2009039873A1/en active Application Filing
  • 2007-09-28 EP EP07818565A patent/EP2198214B1/en not_active Not-in-force
  • 2007-09-28 CN CN200780100863.4A patent/CN101809384B/zh not_active Expired - Fee Related
  • 2007-09-28 DE DE602007013119T patent/DE602007013119D1/de active Active
  • 2007-09-28 DK DK07818565.9T patent/DK2198214T3/da active
  • 2007-09-28 AT AT07818565T patent/ATE501405T1/de not_active IP Right Cessation
• 2010
  • 2010-04-26 NO NO20100598A patent/NO20100598L/no not_active Application Discontinuation

Patent Citations (6)

Non-Patent Citations (1)

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