EP3112776B1 - Kohlendioxidkompressionskälteanlage - Google Patents

Kohlendioxidkompressionskälteanlage Download PDF

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Publication number
EP3112776B1
EP3112776B1 EP16177348.6A EP16177348A EP3112776B1 EP 3112776 B1 EP3112776 B1 EP 3112776B1 EP 16177348 A EP16177348 A EP 16177348A EP 3112776 B1 EP3112776 B1 EP 3112776B1
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Prior art keywords
temperature
carbon dioxide
heat
secondary cooling
cooling device
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EP16177348.6A
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English (en)
French (fr)
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EP3112776A1 (de
Inventor
Mauro Mantovan
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Hiref SpA
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Hiref SpA
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B7/00—Compression machines, plants or systems, with cascade operation, i.e. with two or more circuits, the heat from the condenser of one circuit being absorbed by the evaporator of the next circuit
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B27/00—Machines, plants or systems, using particular sources of energy
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B40/00—Subcoolers, desuperheaters or superheaters
    • F25B40/02—Subcoolers
    • 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
    • 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
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2116—Temperatures of a condenser
    • F25B2700/21163—Temperatures of a condenser of the refrigerant at the outlet of the condenser

Definitions

  • the present invention concerns a carbon dioxide compression refrigeration system.
  • the present invention concerns a refrigeration system designed to be used in a plant/machine for conditioning and/or temperature control and/or refrigeration, of rooms for example, to which the following discussion will explicitly refer without loss of generality.
  • Figure 1 shows an example of a traditional "reverse cycle" refrigeration plant, indicated by I, essentially comprising a closed refrigeration circuit II for circulation of the carbon dioxide, which is provided in turn with: a compressor III designed to compress the carbon dioxide, thus increasing the enthalpy thereof, a cooler IV designed to extract the heat from the previously compressed carbon dioxide, a first expansion valve V designed to maintain the pressure upstream, i.e.
  • a liquid receiver/separator tank VII which is at an intermediate pressure between the evaporation pressure of the carbon dioxide and the first predefined value
  • a second expansion valve VIII designed to cause expansion of the carbon dioxide maintaining the enthalpy constant, thus reducing the temperature and pressure thereof
  • an evaporator IX designed to absorb the heat from the fluid to be cooled by means of the carbon dioxide which evaporates therein.
  • the carbon dioxide is characterized by a critical temperature, i.e. a critical point temperature of approximately 31°C. This temperature is relatively low when compared with the critical temperature of the traditional refrigerant fluids and may therefore be lower than the ambient temperature.
  • the refrigeration system using carbon dioxide shown in Figure 1 may therefore be "transcritical" since release of the negative heat towards the outside, by the cooler IV, is performed at an ambient temperature higher than the critical temperature of the refrigerant fluid. It follows that with conditions being equal, for example the evaporation temperature, the temperature of the carbon dioxide leaving the cooler, the superheating, the overall efficiency of the compression process, the coefficient of performance of a transcritical refrigeration cycle with carbon dioxide is generally lower than a coefficient of performance of a corresponding "subcritical" cycle.
  • the efficiency of a reverse thermodynamic cycle using carbon dioxide is strongly influenced by the temperature thereof at the end of the cooling process, and in particular increases as the temperature decreases.
  • GB 2 525 369 A discloses a refrigeration system which sinks heat to a geothermal heat exchanger and/or an ambient air heat exchanger with a controller regulating a fan speed, geothermal fluid modulating valve and a valve system to selectively interconnect the heat exchangers in series or singularly.
  • GB 2 525 369 A , WO 2006/027330 A1 and WO 2007/022778 A1 disclose a refrigeration system comprising a primary refrigeration circuit that contains carbon dioxide and is provided with:- a compressor device to compress the carbon dioxide,- a primary cooling device, which is designed to perform a first cooling of the carbon dioxide leaving said compressor device so as to extract the heat from the carbon dioxide to cause a drop in the temperature of the carbon dioxide from a first temperature to a second temperature,- expansions means designed to expand the carbon dioxide supplied by the primary cooling device, and- a heat-exchanger device designed to accumulate heat in the expanded carbon dioxide supplied by the expansion means and then supply the carbon dioxide to said compressor device; said system comprising at least one secondary cooling device, which is located downstream of said primary cooling device and upstream of said expansion means, and is designed to perform a second cooling of the carbon dioxide leaving said primary cooling device to cause a further drop in the temperature of the carbon dioxide from said second temperature to a third temperature, lower than said second temperature, before the carbon dioxide is supplied to
  • the Applicant has therefore carried out a detailed study with the objective of identifying a solution relative to a carbon dioxide compression refrigeration system which overcomes the above-mentioned drawbacks, i.e. has an efficiency greater than the carbon dioxide compression systems described above.
  • the object of the present invention is therefore to make available a solution which allows the above objective to be achieved.
  • the number 1 indicates overall a refrigeration system, not forming part of the claimed invention, which is designed to be used in a plant/machine to perform conditioning and/or temperature control and/or refrigeration of a heat-carrying fluid.
  • the heat-carrying fluid can correspond preferably to air, for example, the air of an indoor environment, or water, for example, the water circulating in a plant or a machine.
  • the refrigeration system 1 comprises a closed cycle refrigeration circuit 2 which is adapted, in use, to be crossed by a refrigeration fluid corresponding to carbon dioxide CC2.
  • the refrigeration circuit 2 comprises: a compressor device 3, a primary cooler device 4, an expansion device 5, and a heat exchanger device 6, which are connected to one another in sequence, one after the other, by means of a series of relative connection ducts 7.
  • the heat exchanger device 6 can be arranged in an environment to be cooled or be associated with a hydraulic plant and preferably comprises an evaporator or any similar exchange apparatus, which is designed to accumulate/absorb the heat from the heat-carrying fluid present in the environment or circulating in the hydraulic plant, by means of the previously cooled carbon dioxide in the gaseous state and supplies the carbon dioxide downstream, i.e. at the input to the compressor device 3.
  • the compressor device 3 is designed to compress the carbon dioxide received from the heat exchanger device 6 and supplies it at high pressure to the primary cooling device 4 which provides, in turn, for cooling of the carbon dioxide at high pressure and discharging of the heat absorbed into the external environment.
  • the primary cooler device 4 can be associated with or correspond to an air cooling system or similar systems, and therefore be provided with appropriate cooling fans operated in a known manner by electric devices (electric motors).
  • the primary cooler device 4 receives the incoming carbon dioxide at a first temperature t1 and supplies it outgoing at a second temperature t2 lower than the first temperature t1 (t2 ⁇ t1).
  • the second temperature t2 can be approximately equal to the ambient temperature t0+ ⁇ t0 where ⁇ t0 is a temperature interval depending substantially on the efficiency of the exchange process with the external air.
  • expansion device 5 it is arranged along the refrigeration circuit 2 downstream of the primary cooler device 4 and upstream of the heat exchanger device 6 and can comprise for example an expansion valve or any similar device designed to cause controlled expansion and/or evaporation of the carbon dioxide maintaining the enthalpy constant, thus reducing temperature and pressure.
  • the refrigeration circuit 2 can further comprise preferably, but not necessarily, a flow rate regulator device 8, for a example an expansion valve which is designed to control /maintain the pressure of the carbon dioxide upstream, i.e. leaving the primary cooler device 4, at a first value predefined on the basis of a control signal generated by an electronic control unit 9.
  • a flow rate regulator device 8 for a example an expansion valve which is designed to control /maintain the pressure of the carbon dioxide upstream, i.e. leaving the primary cooler device 4, at a first value predefined on the basis of a control signal generated by an electronic control unit 9.
  • the refrigeration circuit 2 can further comprise, preferably but not necessarily, a liquid receiver/separator tank 12 which is arranged downstream of the flow rate regulator device 8 and is structured so as to contain a given quantity of fluid and separates the carbon dioxide in the gaseous state from the carbon dioxide in the liquid state to supply the latter to the expansion device 5.
  • a liquid receiver/separator tank 12 which is arranged downstream of the flow rate regulator device 8 and is structured so as to contain a given quantity of fluid and separates the carbon dioxide in the gaseous state from the carbon dioxide in the liquid state to supply the latter to the expansion device 5.
  • the refrigeration circuit 2 further appropriately comprises at least one secondary cooling device 10, which is arranged along the refrigeration circuit 2 downstream of the primary cooling device 4 and upstream of the expansion device 5, and is structured to perform a second cooling of the carbon dioxide to supply it outgoing at a third temperature t3 lower than the second cooling temperature t2 (t3 ⁇ t2).
  • the Applicant has found that by further reducing the temperature t of the carbon dioxide supplied leaving the primary cooling device 4, by means of the secondary cooling device 10, a considerable increase in efficiency of the refrigeration system 1 is obtained.
  • the secondary cooling device 10 can be appropriately associated with an external auxiliary heat source 11, which is designed to supply the secondary cooling device 10 with a heat-carrying fluid FT having the fourth temperature t4 to transfer the heat from the carbon dioxide to the heat-carrying fluid FT so as to cause a drop in the temperature of the carbon dioxide at the third temperature t3.
  • the ducts 12, the external auxiliary heat source 11, and the internal duct 10b define an auxiliary cooling circuit 13 designed to extract heat from the carbon dioxide which flows through the duct 10a.
  • the external heat source 11 can be appropriately a natural thermal energy reservoir (infinite reservoir) i.e. present in nature.
  • the natural thermal energy reservoir 11 can be a natural water reservoir 15.
  • the natural water reservoir 15 can advantageously correspond, by choice, to: a water well, a water basin, a lake, a torrent, a river, the sea, groundwater, or any other similar natural reservoir in which the water has the fourth temperature t4.
  • the auxiliary circuit 13 can expediently comprise at least one electric pump 14, which can be arranged along a duct 12 of the auxiliary circuit 13 hydraulically connecting the natural reservoir 15 to the duct 10b, and is designed to supply, under the control of the electronic control unit 9, the water (or a heat-carrying fluid FT associated with the water) at the fourth temperature t4 to the secondary exchanger device 10.
  • the Applicant has found that this solution is extremely simple and inexpensive to produce since it requires, in order to be implemented, only the use of an electric pump and a series of ducts and the secondary exchanger.
  • the external heat source 11 is not limited to the natural water reservoir 15 described above, but alternatively, or additionally, can comprise a ground 16.
  • Figure 6 schematically shows this embodiment, in which the ground 16 can be associated with the secondary cooling device 10 via a geothermal system 17.
  • the geothermal system 17 can comprise, for example, one or more geothermal probes 17a (only one of which is illustrated) connected to the duct 10b via the ducts 12 to supply to the same a heat-carrying fluid FT at the fourth temperature t4 by means, preferably but not necessarily, of the pump 14.
  • the refrigeration system 1 can further comprise a dry cooler 35 consisting, for example, of a water battery provided with cooling fans.
  • the dry cooler 35 is designed to be selectively connected to the probe 17 in such a way that the heat source 16, i.e. the ground, can be thermally regenerated.
  • the Applicant has found that regeneration of the ground is particularly expedient to avoid a reduction in efficiency of the system 1 caused by the thermal drift of the ground.
  • the system 1 temporarily connects the dry cooler 15 to the probe/s 17 preferably according to the temperature of the ground and/or the temperature of the heat-carrying fluid FT and at the same time excludes the geothermal probe 17a from the thermal exchange with the secondary exchanger 10.
  • the system 1 can be provided with at least one three-way valve 42 or any similar apparatus, which is arranged along a relative duct 12 and is configured to connect, by command, the probe 17 to the second cooling device 10 or alternatively to the dry cooler 15.
  • the external heat source 11 could further comprise, alternatively or additionally to the solutions described above, an adiabatic cooling device 18.
  • the adiabatic cooling device 18 can preferably integrate/comprise the secondary cooling device 10.
  • the adiabatic cooling device 18 can comprise a box-type metal frame provided with through slits (not illustrated), an evaporator device (not illustrated) defined by a wet pack/evaporator arranged inside the frame, and fan devices (not illustrated) which are coupled to the frame in the area of through openings obtained on the frame and are designed to circulate air inside the frame, thus passing through the wet pack/evaporator.
  • the secondary cooling device 10 can also be arranged/integrated. In use, the flow of air generated by the fans passes through the wet pack/evaporator. The air extracted releases heat to the water of the pack which, by evaporating, causes saturation of the air, lowering the temperature thereof to the fourth temperature t4.
  • the flow of air at the fourth temperature t4 is then pushed towards the secondary cooling device 10 and in particular towards its duct 10a thus determining additional cooling of the carbon dioxide circulating in the duct 10a which therefore drops to the third temperature t3.
  • the adiabatic cooling device 18 is not limited to the solution described above but could comprise any similar adiabatic air cooling equipment.
  • a cooling device which, instead of being provided with the wet pack/evaporator, is provided with nozzles (not illustrated) designed to generate water, preferably nebulized.
  • the nebulized water generated by the nozzles is crossed by the air extracted by the fans and causes therein a lowering of the temperature to the fourth temperature t4.
  • the air cooled to the fourth temperature t4 is then pushed/blown towards the secondary cooling device 10 thus striking the duct 10a and therefore determining the second cooling of the carbon dioxide circulating in the duct 10a.
  • the adiabatic cooling device 18 instead of performing direct cooling of the carbon dioxide by means of the air previously cooled (according to the procedure described above), carries out indirect cooling of the carbon dioxide by means of the heat-carrying fluid circulating through the auxiliary cooling circuit 13.
  • the adiabatic cooling device 18 can be associated with the auxiliary cooling circuit 13 so as to perform "air" adiabatic cooling of the heat-carrying fluid FT, for example the water, and cause release of the heat from the carbon dioxide to the heat-carrying fluid FT inside the secondary cooling device 10.
  • the external heat source 11 could further comprise, alternatively or in addition to the solutions described above, at least one evaporation tower 19 or cooling tower with forced circulation and/or induced flow (not illustrated).
  • the evaporation tower is known and will not be further described, or only to specify that it can have nozzles at the top designed to emit jets of water inside the tower, and is provided, at its base, with a container or well which is designed to collect the water emitted by the nozzles. In use, the water emitted by the nozzles is cooled by the air which rises due to the chimney effect or owing to the presence of fans. The cooled water therefore precipitates towards the base of the tower inside the container.
  • the secondary cooling device 10 can be associated with the cooled water container in the tower.
  • the duct 10a could be arranged inside the container so as to be immersed and therefore in contact with the cooled water.
  • the external auxiliary heat source 11 could comprise a tank 29 of heat-carrying fluid FT, which is hydraulically connected to the secondary cooling device 10 to circulate in the same the heat-carrying fluid FT, and contains phase change materials (PCM) which, in use, are designed to cool the heat-carrying fluid FT.
  • PCM phase change materials
  • PCMs are materials used for storing thermal energy in the form of latent heat. Release and absorption of the energy occurs during the phase change, when the latent solidification and liquefaction heat is exploited around a constant temperature characteristic of each material. In this specific case, the PCM passes from the solid state to the liquid state receiving the heat coming from the CO2 cycle.
  • the tank 29 can be structured so that the heat exchange between the phase change materials and the heat-carrying fluid FT inside it occurs via a direct or indirect contact.
  • the tank 29 can be structured so that the phase change materials remain in use partially or completely immersed in the heat-carrying fluid FT.
  • the tank 29 could comprise an internal hydraulic duct (for example one or more probes or coil section/s or similar) arranged in thermal contact (coupled) with the phase change materials.
  • the duct can contain the refrigerant itself and therefore constitute the exchanger 10.
  • phase change materials are designed to release or absorb energy in the form of latent heat, during the phase change from liquid to solid and vice versa.
  • the amount of heat exchanged during the phase change is much greater than the sensible amount exchanged, and this makes these materials conveniently suitable for storing thermal energy.
  • the phase change materials can be enclosed in containers positioned inside the tank 29.
  • the phase change material containers can be arranged in the tank 29 so as to be in direct contact with the heat-carrying fluid (immersed in the fluid) or in indirect contact (the fluid flows inside a coil) .
  • the cooled heat-carrying fluid then in turn cools the carbon dioxide circulating through the secondary cooling device 10.
  • transition of the phase change materials occurs, from the solid state to the liquid state and, during the transition, the materials absorb heat from the heat-carrying fluid FT and appropriately cool it.
  • phase change materials since they are characterized by a constant temperature useful for cooling the CO2 to the target temperature.
  • the secondary cooling device 10 can be associated with and/or contain an auxiliary cooling device 20 of an external auxiliary refrigeration plant 21.
  • the external auxiliary refrigeration plant 21 can perform a reverse thermal cycle, for example corresponding to a heat pump for heating utilities, and comprise, in addition to the auxiliary cooler device 20 containing for example the duct 10b, an auxiliary compressor device 22, an auxiliary heat exchanger device 23, and an auxiliary expansion device 24 connected in sequence to one another by means of ducts 25 through which a refrigerant fluid circulates.
  • the performance of a reverse thermal cycle by the external auxiliary refrigeration plant 21 is known and substantially equivalent to the cycle implemented by the refrigeration plant shown in Figure 1 and consequently will not be further described, or only to specify that the auxiliary heat exchanger device 23 can be air or water operated and, in use, is crossed by the heat-carrying fluid FT having the fourth temperature t4.
  • the auxiliary heat exchanger device 23 can be coupled to the secondary cooling device 10 so that the heat of the carbon dioxide circulating in the duct 10a is released to the heat-carrying fluid FT circulating in the auxiliary heat exchanger device 20.
  • the refrigeration system 1 can be provided with an electronic temperature detection system, which is designed to supply the electronic control unit 9 with electrical signals indicative of the temperature t4 of the heat-carrying fluid FT supplied by the external heat source 11, the temperature of the heat-transfer fluid FT supplied by the adiabatic cooling device 18, and the temperature t2 of the carbon dioxide supplied at the outlet of the main cooling device 4.
  • an electronic temperature detection system which is designed to supply the electronic control unit 9 with electrical signals indicative of the temperature t4 of the heat-carrying fluid FT supplied by the external heat source 11, the temperature of the heat-transfer fluid FT supplied by the adiabatic cooling device 18, and the temperature t2 of the carbon dioxide supplied at the outlet of the main cooling device 4.
  • the electronic temperature detection system could comprise temperature sensors 26 which can be arranged: at the outlet of the main cooling device 4 to supply a signal tm2 indicative of the temperature t2 of the carbon dioxide supplied at the outlet of the main cooling device 4; at the natural water reservoir 15 (if used in this embodiment) to supply a signal tms indicative of the temperature of the heat-carrying fluid FT corresponding to or associated with the water; at the geothermal system 16 (if used in this embodiment) to supply a signal tms indicative of the temperature of the heat-carrying fluid FT cooled by the ground; at the adiabatic cooling device (if used in this embodiment) to supply a signal tms indicative of the temperature of the air or of the cooling water; at the evaporation tower 19 to supply a signal tms indicative of the temperature of the heat-carrying fluid FT associated with the water cooled in the tower; at the tank 29 provided with the phase change materials (if used in this embodiment) to supply a signal tms indicative of the
  • the refrigeration system 1 can be provided preferably with a by-pass duct 27 which connects the outlet of the primary cooling device 4 to the outlet of the secondary cooling device 10, and valve means 28, for example an electrically operated three-way valve, designed to connect, on the basis of a control signal, the outlet of the primary cooling device 4 to the inlet of the secondary cooling device 10 or, alternatively, to the inlet of the flow rate regulator device 8 thus by-passing the secondary cooling device 10.
  • valve means 28 for example an electrically operated three-way valve, designed to connect, on the basis of a control signal, the outlet of the primary cooling device 4 to the inlet of the secondary cooling device 10 or, alternatively, to the inlet of the flow rate regulator device 8 thus by-passing the secondary cooling device 10.
  • the electronic control unit 9 can be configured so as to determine the temperature t2 downstream of the main cooling device 4 on the basis of the temperature measured tm2 supplied by the measurement sensors 26, determine the temperature t4 on the basis of the temperature measured tms, compare the temperature t2 with a target temperature tob, compare the temperature t2 with the temperature t4, and control the valve means 28 on the basis of the outcome of said comparisons.
  • the electronic control unit 9 controls the valve means 28 so as to establish communication with the outlet of the primary cooling device 4 at the inlet of the secondary cooling device 10 thus providing the second cooling of the carbon dioxide when a first and a second condition occur/are met, in which the first condition is met/occurs when the temperature t2 is greater than the target temperature (t2>tob) while the second condition is met/occurs when the temperature t2 is greater than the temperature t4.
  • the electronic control unit 9 controls the valve means 28 so as to establish communication with the outlet of the primary cooling device 4 at the outlet of the secondary cooling device 10 thus excluding the latter from the refrigeration circuit 2.
  • the operation of the refrigeration system 1 according to the various embodiments described above can be easily deduced from the above and consequently will not be further described.
  • the use of a secondary cooling device downstream of the primary cooling device traditionally present in reverse cycle refrigeration plants allows the temperature of the carbon dioxide to be further lowered before supplying it at the inlet to the expansion valve and to the heat exchanger device, thus conveniently increasing the plant efficiency.
  • the embodiment illustrated in Figure 4 is relative to an embodiment variation of the present invention and corresponds to a refrigeration system 30, which is similar to the refrigeration system 1, the component parts of which will be indicated, where possible, by the same reference numbers as those indicating corresponding parts of the refrigeration system 1.
  • the refrigeration system 30 differs from the refrigeration system 1 due to the fact that it comprises a plurality of external heat sources 11, which contain respective heat-carrying fluids FTi and are connected to the secondary cooling device 10 by means of a hydraulic circuit 31 which is structured to selectively establish communication between the external heat sources 11 and the secondary cooling device 10, thus selectively supplying to the latter the heat-carrying fluid Fti of the external heat source 11 selected.
  • the hydraulic circuit 31 can comprise a series of electrically operated on-off valves 32, expediently arranged along relative ducts 12 which connect the external heat sources 11 to the secondary cooling device 10, while the measurement sensors 26 supply to the electronic control unit 9 an electric signal indicative of the temperature tmsi (i, between 1 and n, is the number of sources) associated with the fourth temperature t4 of the relative heat-carrying fluid FTi.
  • the electronic control unit 9 can be configured so as to receive the temperatures tmsi, compare the temperatures tmsi with each other, determine the external heat source 11 with lower temperature tmsi on the basis of the comparison, and operate the valves 32 when the first and second condition occur, so as to associate with the secondary cooling device 10 the external heat source 11 determined, i.e. having lower temperature tmsi and therefore exclude the remaining external heat sources 11.
  • the electronic control unit 9 can monitor continuously or at predefined intervals the temperatures tmsi of the external heat sources 11 and operate the valves 32 to switch/deviate the connection of the secondary cooling device 10 from a current external heat source 11 to another external heat source 11 having a temperature t4 lower than the temperature t4 of the remaining external heat sources 11 and in particular the one supplying the secondary cooling device 10.
  • the electronic control unit 9 operates the valves 32 to connect to the secondary cooling device 10 the most appropriate external heat source 11, i.e. the one having a temperature t4 lower than the other sources 11, and if the first and second condition are met, it operates the valve 28 to perform the second cooling of the carbon dioxide to supply it at the outlet at the third temperature t3.
  • the embodiment illustrated in Figure 5 concerns an embodiment variation relative to a refrigeration system 40, which is similar to the refrigeration systems 1 and 30, and the component parts of which will be indicated, where possible, by the same reference numbers as those that indicate corresponding parts of the refrigeration systems 1 and 30.
  • the refrigeration system 40 differs from the refrigeration systems 1 and 30 due to the fact that it comprises a plurality of secondary cooling devices 10 each of which is associated with a respective external heat source 11, a plurality of by-pass ducts 27 each of which is associated with a corresponding secondary cooling device 10, and a plurality of valve means 28, for example three-way valves, each of which is arranged along a section of duct 7 connected to the inlet of each secondary cooling device 10 and is designed to connect by command the section of duct 7 to the inlet of the secondary cooling device 10 or, alternatively, to the inlet of the by-pass duct 27 thus excluding the secondary cooling device 10 from the passage of the carbon dioxide, then supplying the latter directly downstream of the secondary cooling device 10.
  • the electronic control unit 9 is configured so as to receive the temperatures tmsi, compare the temperatures tmsi with one another, determine the external heat source 11 which has the lowest temperature tmsi on the basis of the comparison, and operate the valve means 28 when the first and second condition are met, so as to operate the secondary cooling device 10 associated with the external heat source 11 determined, i.e. presenting the lowest temperature tmsi thus excluding the remaining secondary cooling devices 10 from the refrigeration circuit 2.
  • the electronic control unit 9 can control the valve means 28 so that the secondary cooling devices 10 are individually and alternatively connected/included in the refrigeration circuit 2, one after the other on the basis of the temperatures tmi measured.
  • the secondary cooling devices 10 can be selectively connected to the refrigeration circuit 2 according to a decreasing sequential order of temperatures measured ti. In this way, the carbon dioxide is cooled when it sequentially passes through the secondary cooling devices 10 by means of heat-carrying fluids Fti which have progressively decreasing temperatures measured tmsi.
  • the refrigeration system 1 can be structured so that the arrangement of the secondary cooling devices 10 along the section 7 which connects the outlet of the main cooling device 4 to the inlet of the flow rate regulating device 8 is such as to ensure that the carbon dioxide sequentially passes through the secondary cooling devices 10 according to an order of decreasing temperatures t4.
  • the three secondary cooling devices 10 are arranged along the section 7 so that the carbon dioxide leaving the main cooling device 4 passes in sequence through the first secondary cooling device 10 having the temperature t4' ⁇ t3, the second secondary cooling device 10 having the temperature t4" ⁇ t4' and the third secondary cooling device 10 having the temperature t4′′′ ⁇ t4" .
  • the secondary cooling devices 10 can therefore be conveniently exploited individually, allowing exchange with one single external heat source 11, or in series according to the relative temperatures.
  • This embodiment conveniently increases the efficiency of the refrigeration system 1 since it allows the carbon dioxide to undergo a series of heat exchanges, in which each heat exchange is performed on the basis of a temperature difference between the carbon dioxide and the heat-carrying fluid supplied by the relative external heat source 11 which, thanks to the multiple exchange, is considerably reduced.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
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  • General Engineering & Computer Science (AREA)
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  • Chemical Kinetics & Catalysis (AREA)
  • Other Air-Conditioning Systems (AREA)

Claims (8)

  1. Ein Kühlsystem (40), das einen primären Kühlkreislauf (2) umfasst, der Kohlendioxid erhält und ausgestattet ist mit:
    - einer Kompressorvorrichtung (3) zum Komprimieren des Kohlendioxids,
    - einer primären Kühleinrichtung (4), die so ausgelegt ist, dass sie eine erste Kühlung des die Kompressoreinrichtung (3) verlassenden Kohlendioxids durchführt, um dem Kohlendioxid die Wärme zu entziehen und einen Temperaturabfall des Kohlendioxids von einer ersten Temperatur (t1) auf eine zweite Temperatur (t2) zu erzielen,
    - einer Expansionseinrichtung (5), die dazu dient, das von der primären Kühlvorrichtung (4) zugeführte Kohlendioxid zu expandieren, und
    - einer Wärmetauschervorrichtung (6), die so ausgebildet ist, dass sie Wärme in dem von den Expansionsmitteln (5) zugeführten expandierten Kohlendioxid akkumuliert und das Kohlendioxid dann der Kompressorvorrichtung (3) zuführt;
    wobei das System (1) außerdem umfasst:
    - externe Hilfswärmequellen (11),
    - eine Vielzahl von sekundären Kühlvorrichtungen (10), die stromabwärts der primären Kühlvorrichtung (4) und stromaufwärts der Expansionsmittel (5) angeordnet sind und so ausgestaltet sind, dass sie eine zweite Kühlung des die primäre Kühlvorrichtung (4) verlassenden Kohlendioxids durchführen, um die Temperatur des Kohlendioxids von der zweiten Temperatur (t2) auf eine dritte Temperatur (t3) zu senken, die niedriger ist als die zweite Temperatur (t2), bevor das Kohlendioxid den Expansionsmitteln (5) zugeführt wird, wobei jede der sekundären Kühlvorrichtungen (10) mit einer entsprechenden externen Hilfswärmequelle (11) verbunden ist,
    - wobei die sekundären Kühlvorrichtungen (10) hintereinander in Reihe geschaltet und thermisch/hydraulisch mit den jeweiligen externen Hilfswärmequellen (11) verbunden sind, die so ausgebildet sind, dass sie die sekundären Kühlvorrichtungen (10) mit einem wärmetragenden Fluid (FTi) versorgen, das vierte Temperaturen (t4) aufweist, die niedriger als die dritte Temperatur (t3) sind, um Wärme von dem Kohlendioxid auf das wärmetragende Fluid (FTi) zu übertragen und so die Temperatur des Kohlendioxids auf die dritte Temperatur (t3) zu senken,
    - eine Vielzahl von Bypass-Leitungen (27), von denen jede mit einer entsprechenden sekundären Kühlvorrichtung (10) verbunden ist, eine Vielzahl von Ventilmitteln (28), die gesteuert werden können, um die zweite Kühlung des Kohlendioxids mittels der einen oder mehreren sekundären Kühlvorrichtungen (10) durchzuführen; wobei jedes der Ventilmittel (28) entlang eines Abschnitts eines Kanals (27) angeordnet ist, der mit dem Einlass jeder sekundären Kühlvorrichtung (10) verbunden ist, und so ausgeführt ist, dass er durch Steuerung den Abschnitt des Kanals (27) mit dem Einlass der sekundären Kühlvorrichtung (10) oder alternativ mit dem Einlass des Bypass-Kanals (27) verbindet, um die sekundäre Kühlvorrichtung (10) vom Durchgang des Kohlendioxids auszuschließen und letzteres dann direkt stromabwärts der sekundären Kühlvorrichtung (10) zuzuführen,
    - elektronische Steuermittel (9) und
    - Messfühler (26), die den elektronischen Steuermitteln (9) ein elektrisches Signal liefern, das für die Temperaturen (tmsi) repräsentativ ist, die den wärmetragenden Fluiden (FTi) der externen Zusatzwärmequellen (11) zugeordnet sind
    - die Messfühler (26) außerdem Temperaturfühler (26) umfassen, die am Ausgang der primären Kühlvorrichtung (4) angeordnet sind, um ein Signal (tm2) zu liefern, das die zweite Temperatur (t2) anzeigt,
    die elektronischen Steuermittel (9) so ausgelegt sind, dass sie:
    - die Temperaturen (tmsi), die den wärmetragenden Fluiden (FTi) der externen Hilfswärmequellen (11) zugeordnet sind, miteinander vergleichen,
    - die externe Hilfswärmequelle (11) bestimmen, die auf der Grundlage des Vergleichs die niedrigste Temperatur (tmsi) aufweist,
    - das Ventilmittel (28) steuern, wenn eine erste und eine zweite Bedingung erfüllt sind, um die Kühlvorrichtung (10) zu betreiben, die mit den externen Quellen (11) verbunden ist, die die niedrigste Temperatur (tmsi) aufweisen, wodurch die übrigen sekundären Kühlvorrichtungen (10) vom Kühlkreislauf ausgeschlossen werden,
    - die erste Bedingung ist erfüllt, wenn die zweite Temperatur (t2) größer als eine Zieltemperatur (tob) ist;
    - die zweite Bedingung ist erfüllt, wenn die zweite Temperatur (t2) höher ist als die vierte Temperatur (t4).
  2. Kühlsystem nach Anspruch 1, wobei eine externe Hilfswärmequelle (11) mindestens ein natürliches Wasserreservoir (15) umfasst, das ein wärmetragendes Fluid (FT) enthält, das Wasser entspricht oder mit diesem thermisch verbunden ist.
  3. Kühlsystem nach Anspruch 1, wobei die externe Hilfswärmequelle (11) einen Untergrund (16) und ein mit dem Untergrund (16) verbundenes geothermisches Kühlsystem (17) zur Kühlung des wärmetragenden Fluids (FT) umfasst.
  4. Kältesystem nach Anspruch 1, wobei die externe Hilfswärmequelle (11) mindestens eine adiabatische Luft-Wasser-Kühlvorrichtung (18) zur Kühlung des Wärmeträgerfluids (FT) umfasst.
  5. Kühlsystem nach Anspruch 1, wobei die externe Hilfswärmequelle (11) Kühlmittel mit Phasenwechselmaterialien (PCM) umfasst.
  6. Kühlsystem nach Anspruch 1, wobei die elektronischen Steuermittel (9) so ausgebildet sind, dass sie die Ventilmittel (28) steuern, um die sekundären Kühleinrichtungen (10) mit dem Kühlkreislauf (2) zu verbinden, um zu bewirken, dass das Kohlendioxid durch die sekundären Kühleinrichtungen (10) in der Reihenfolge der abnehmenden Temperaturen der jeweiligen wärmetragenden Fluide (FT) strömt.
  7. Kühlsystem nach Anspruch 1, wobei die elektronischen Steuermittel (9) so ausgebildet sind, dass sie die Ventilmittel (28) so steuern, dass die sekundären Kühleinrichtungen (10) einzeln und alternativ nacheinander auf der Grundlage der gemessenen Temperaturen (tmsi) mit dem primären Kühlkreislauf (2) verbunden/eingeschlossen werden.
  8. Kühlsystem nach Anspruch 7, wobei die elektronischen Steuermittel (9) so konfiguriert sind, dass sie die sekundären Kühleinrichtungen (10) selektiv mit dem primären Kühlkreislauf (2) gemäß einer abnehmenden sequentiellen Reihenfolge der gemessenen Temperaturen verbinden, um zu bewirken, dass das Kohlendioxid gekühlt wird, wenn es sequentiell die sekundären Kühleinrichtungen (10) mittels wärmetragender Fluide (Fti) passiert, die progressiv abnehmende gemessene Temperaturen (tmsi) aufweisen.
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