Refrigeration system

Description

[0001] The present patent application claims priority from French patent application FR17 / 57207. Domain

[0002] This application concerns a refrigeration installation. Exposition of prior art

[0003] A refrigeration system can be used in many different applications.

[0004] An example of the use of a refrigeration installation concerns an air conditioning system, particularly within the framework of an urban cooling network or for a data center.

[0005] Another example of the use of a refrigeration system concerns an artificial snow production system, for example for snowmaking in ski resorts in the case of low snowfall due to weather conditions or inherent to the geographical location of the resorts.

[0006] In general, for any thermomechanical energy converter, and particularly for a refrigeration system, the coefficient of performance (COP) is the ratio between the thermal power produced by the system (quantity of hot heat Q+ hp or quantity of cold heat Q ref) and the work supplied to the system (work W). It is generally desirable for the COP to be as high as possible, which reflects good energy efficiency of the system and results in low energy consumption, bearing in mind that energy consumption includes the system's electrical consumption.

[0007] There are various types of refrigeration systems that can be used, particularly in artificial snow production systems. The first type of artificial snow production system is open to ambient air, such as snow cannons or snow poles, and generally involves spraying a mixture of water and air that crystallizes upon contact with the ambient air. The air may come from a compressed air source, the expansion of which causes snow formation. A drawback of these systems is that they can only operate within limited temperature and humidity ranges, generally below -2°C and above 30% humidity. A second type of artificial snow production system includes open systems, such as those described in patent application WO2012 / 104787.The electricity consumption of such snowmaking systems typically ranges from 20 kWh to 40 kWh per cubic meter of snow produced, which is lower than that of second- and third-generation snowmaking systems. However, such systems require the construction of cooling towers and therefore have a construction cost that is too high for large-scale operation.

[0008] Third-party artificial snow production systems include closed-loop, refrigerator-type systems with a compressor, condenser, expansion valve, and evaporator. A drawback is that the COP (Coefficient of Performance) is generally low, typically in the range of 2 to 4. Furthermore, the electricity consumption of such snow production systems can be high, for example, from 40 kWh to 120 kWh per cubic meter of snow produced.

[0009] Fourth-generation artificial snow production systems include closed systems employing cryogenic processes, notably the formation of a mixture of water and a cryogenic gas, such as nitrogen or carbon dioxide. While the COP (Coefficient of Performance) of such a snow production system can be high, the energy required to produce the cryogenic fluid must be taken into account. Consequently, the overall energy consumption of such snow production systems can exceed several hundred kWh per cubic meter of snow produced, resulting in prohibitively high operating costs for large-scale use and significant logistical challenges.

[0010] It would be advisable to design a refrigeration system, particularly for air conditioning or artificial snowmaking systems, with a high COP (Coefficient of Performance), ideally above 6 and preferably above 10, and low power consumption, especially when the refrigeration unit is installed in a snowmaking system with a consumption of less than 5 kWh, preferably less than 3 kWh per cubic meter of snow produced. Furthermore, it would be desirable for the refrigeration unit to operate normally over a wide range of ambient temperatures, particularly above freezing, and preferably up to 25°C, or even up to 35°C.

[0011] Document JP 2004 251541 A discloses a refrigeration installation according to the preamble of claim 1. Summary

[0012] Thus, one objective of an embodiment is to at least partially overcome the disadvantages of the refrigeration installations described above.

[0013] Another objective of an embodiment is that the COP of the refrigeration installation is greater than 6, preferably greater than 10.

[0014] Another objective of an embodiment is that the electrical consumption of the refrigeration system is reduced, in particular, when the refrigeration system is installed in a snow production system, to less than 5 kWh per cubic meter of snow produced, preferably less than 3 kWh per cubic meter of snow produced.

[0015] Another objective of an embodiment is that the refrigeration installation can operate at an ambient temperature between -30 °C and +25 °C, preferably between -30 °C and +35 °C.

[0016] Another objective of one embodiment is that the cost of constructing the refrigeration installation is reduced.

[0017] Thus, the invention provides for a refrigeration installation according to the subject of claim 1.

[0018] According to one embodiment, the installation includes a device for heating water in the gaseous state in the first enclosure intended to supply the compression device.

[0019] According to the invention, the first enclosure further contains water in a solid state at a temperature less than or equal to the triple point temperature of water.

[0020] According to one embodiment, the water circulates in a closed loop within the installation.

[0021] According to one embodiment, the condensation device includes a first heat exchanger outside the second enclosure and means for circulating a first heat transfer fluid around the second enclosure through the first heat exchanger.

[0022] According to one embodiment, the first heat transfer fluid is ambient air or water from a stream, body of water or water table.

[0023] According to one embodiment, the second pressure in the second enclosure is less than or equal to 10000 Pa (100 mbar), preferably less than or equal to 6000 Pa (60 mbar).

[0024] According to one embodiment, the cold power extraction device includes a hydraulic circuit in which some or all of the liquid water present in the first enclosure circulates, the hydraulic circuit including a second heat exchanger located outside the first enclosure.

[0025] According to one embodiment, the cold power extraction device comprises a closed hydraulic circuit in which a second heat transfer fluid circulates, the hydraulic circuit comprising a second heat exchanger located outside the first enclosure and a third heat exchanger disposed in the first enclosure.

[0026] According to one embodiment, the refrigeration installation includes a third enclosure in which the second heat exchanger is located, delivering the cooling power to the end user, the third enclosure containing, for example, water in a solid state.

[0027] According to one embodiment, the heating device includes a source of infrared radiation and / or a source of microwave radiation.

[0028] According to one embodiment, the heating device is adapted to heat the water in the gaseous state in the first enclosure intended to supply the compression device by at least 2 °C, preferably by at least 10 °C, more preferably by at least 20 °C.

[0029] According to the invention, the compression device comprises at least one turbomachine-type compressor, in particular a centrifugal compressor and / or an axial compressor.

[0030] According to the invention, the compression device comprises a succession of stages, each stage comprising a rotor and a stator.

[0031] According to one embodiment, the compression device is a Tesla compressor.

[0032] According to the invention, the compression device comprises a first stage compressor with a fixed compression ratio and a second stage compressor with a controllable compression ratio.

[0033] According to one embodiment, the refrigeration installation further includes, in the first enclosure, a mechanical device for protecting the compression device against the admission of particles in solid and / or liquid state.

[0034] According to one embodiment, the refrigeration installation includes a supply line for water in liquid state into the first enclosure.

[0035] According to one embodiment, the condensation device includes at least one nozzle for projecting droplets of water in liquid state into the second enclosure.

[0036] According to one embodiment, the installation further includes a system for regulating the pressure difference between the second chamber and the first chamber.

[0037] According to one embodiment, the control system includes an expansion turbine configured to expand water in the gaseous state from the second enclosure and pump a mixture containing water in the gaseous state and water in the liquid state back into the first enclosure.

[0038] According to one embodiment, the first enclosure comprises at least one reservoir of water in a liquid state and into which said mixture is pumped into the water in a liquid state contained in said reservoir.

[0039] One embodiment also provides for an artificial snow production system including a refrigeration installation as defined above.

[0040] One embodiment also provides for an air conditioning system for industrial, collective and private installations including a refrigeration installation as defined above, particularly within the framework of an urban cooling network or for a data center.

[0041] The invention also provides a method for producing cold according to the subject of claim 14.

[0042] According to one embodiment, the process further includes the step of heating water in a gaseous state in the first enclosure intended to be compressed. Brief description of the drawings

[0043] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the attached figures, among which: there figure 1is a partial, schematic cross-sectional view of one embodiment of a refrigeration system; the figures 2 to 4 represent water enthalpy-pressure diagrams illustrating the operation of the refrigeration system shown in figure 1 ; there figure 5 is a partial, schematic cross-sectional view of a more detailed embodiment of part of the refrigeration system of the figure 1 ; THE figures 6 and 7 These are partial, schematic cross-sectional views of more detailed embodiments of another part of the refrigeration system. figure 1 ; there figure 8 is a partial, schematic cross-sectional view of another embodiment of a refrigeration system; the figure 9 is a partial, schematic cross-sectional view of a more detailed embodiment of part of the refrigeration system of the figure 8 ; and the Figure 10is a partial and schematic cross-sectional view of another embodiment of a refrigeration installation. Detailed description

[0044] For clarity, the same elements have been designated by the same references in the various figures, and furthermore, the various figures are not drawn to scale. In addition, only the elements necessary for understanding this description have been shown and are described. In particular, compressors and heat exchangers are well known to those skilled in the art and are not described in detail. In the following description, when referring to relative positional qualifiers, such as "above," "below," "superior," "inferior," etc., or orientational qualifiers, such as "horizontal," "vertical," etc., this refers to the orientation of the figures or to a refrigeration unit in its normal operating position.In the rest of the description, unless otherwise stated, the terms "approximately", "about", "roughly" and "in the order of" mean "within 10%", preferably "within 5%".

[0045] In the remainder of this application, "water" refers to the chemical compound H₂O, which can be in a liquid, solid, or gaseous state. Furthermore, the terms "water in a gaseous state" and "water vapor" are used interchangeably hereafter. In the remainder of this application, the terms "liquid water" and "water in a liquid state" are used interchangeably to refer to pure water in a liquid state or to water in a liquid state corresponding to the solvent of an aqueous solution containing at least one other solute. Moreover, in the remainder of this description, the term "triple point of water" means "triple point of pure water."

[0046] Embodiments of refrigeration systems using water in the liquid state will now be described. It is clear that, in these embodiments, the water in the liquid state can correspond to the solvent of an aqueous solution, that is to say, additives can be added to the water in the liquid state.

[0047] There figure 1 represents a method of implementing a refrigeration installation 5.

[0048] Refrigeration unit 5 includes: a first low-pressure enclosure 10, gas-tight with respect to the external environment and thermally insulated with respect to the external environment, the first low-pressure enclosure 10 containing, in operation, essentially water vapor 11; a tank 12 containing liquid water 14, and, during steady-state operation of the refrigeration system 5, water in a solid state 15, the tank 12 being located in the first low-pressure enclosure 10 and being open to the internal volume of the first low-pressure enclosure 10; a liquid water supply line 18 to the tank 12; a protective element 20, housed in the first low-pressure enclosure 10, covering the free surface of the liquid water 14 and preventing the projection of liquid water splashes outside the tank 12; at least one heating device 22 for at least part of the water vapor in the first low-pressure enclosure 10;a cold power extraction device 24 in the tank 12, for example a solid water recovery device connected to the tank 12; a second low-pressure enclosure 30, gas-tight with respect to the outside environment and thermally insulated with respect to the outside environment, the pressure in the second low-pressure enclosure 30 being greater than the pressure in the first low-pressure enclosure 10; a compressor 32, also called a compression device, for example a turbocharger, a turbine or a Tesla compressor, connecting the first low-pressure enclosure 10 to the second low-pressure enclosure 30, strictly receiving water vapor from the first low-pressure enclosure 10 and supplying compressed water vapor to the second low-pressure enclosure 30;a condensation device 34, also called condenser 34, adapted to liquefy the water vapor present in the second low-pressure enclosure 30, the condenser 34 being partly housed in the second low-pressure enclosure 30 and comprising, for example, a heat exchanger cooled by ambient air, the condenser 34 comprising means, for example, a fan 36, for circulating ambient air through the heat exchanger; a line 38 for recovering the liquid water produced by the condenser 34; and a processing module 40 connected to the heating device 22, the compressor 32 and the condenser 34 and adapted to control the heating device 22, the compressor 32 and the condenser 34.

[0049] When the refrigeration system 5 operates in open cycle, the liquid water 14 contained in the tank 12 can be water directly from the mains water supply system, or fresh water, in particular water from a stream or a reservoir. When the refrigeration system 5 operates in closed cycle, the line 38 can be connected to the line 18. The refrigeration system 5 may also include a system 42 for regulating the pressure difference between the second low-pressure chamber 30 and the first low-pressure chamber 10. The system 42 may be a controlled valve system, a capillary tube system, an expansion turbine system, or a weir system, and is adapted to maintain the pressure difference between the second low-pressure chamber 30 and the first low-pressure chamber 10 at a substantially constant value.

[0050] The processing module 40 may be a dedicated circuit or may include a processor, for example a microprocessor or a microcontroller, adapted to execute instructions from a computer program stored in memory. The refrigeration system 5 may also include sensors, including temperature sensors, pressure sensors, level sensors, flow sensors, etc., not shown, connected to the processing module 40, particularly for detecting temperature and pressure in chambers 10 and 30.

[0051] In one embodiment, the compressor 32 is an axial or centrifugal compressor that delivers a flow of compressed vapor substantially along the compressor's axis of rotation. The compressor comprises a series of compression stages, each stage including a rotor and a stator. The rotor has blades driven in rotation by a drive shaft. The rotor accelerates the gas flow using the energy transmitted by the compressor's drive shaft. The stator has stationary blades. The stator converts the kinetic energy of the gas flow into pressure via its shape.

[0052] The heating device 22 is preferably a radiant heating device, comprising a source of electromagnetic radiation reaching the water vapor. The heating device 22 includes, for example, an infrared water vapor heating system or, for example, a microwave water vapor heating system. In one embodiment, the heating device 22 comprises both an infrared radiation source and a microwave radiation source. Depending on the intended application, the heating device 22 may not be present.

[0053] The dimensions of the refrigeration system 5 depend on the intended application. The volume of the first low-pressure chamber 10 can range from 1 liter to several thousand cubic meters, in particular from 10 liters to 10,000 liters. The volume of the second low-pressure chamber 30 can range from 1 liter to one thousand cubic meters, in particular from 1 liter to 10,000 liters. The volume of liquid water 14 in the tank 12 can range from 1 liter to several thousand cubic meters, in particular from 1 liter to 3,000 m³, and especially from 9 liters to 9,999 liters.

[0054] The refrigeration installation 5 includes a primary vacuum pump, not shown, connected to the first low-pressure chamber 10 and / or to the second low-pressure chamber 30.

[0055] There figure 2 represents an enthalpy-pressure diagram of water illustrating the operation of the refrigeration system 5 at the beginning of its operation.

[0056] The reference points A to G in figure 2 illustrate successive states through which water passes circulating in the refrigeration system 5.

[0057] Point A represents liquid water that will be introduced into tank 12 via pipe 18, for example, to fill tank 12 at the start of operation of system 5. The pressure of the liquid water at point A has a first pressure value, and the temperature of the liquid water at point A has a first temperature value. In one embodiment, the first pressure value is greater than or equal to 0.1 MPa (1 bar), for example, greater than or equal to 0.1 MPa (1 bar) and less than or equal to 10 MPa (100 bar). In another embodiment, the first temperature value is greater than or equal to 5 °C, for example, greater than or equal to 5 °C and less than or equal to 10 °C. The water supplied to tank 12 comes, for example, from a water distribution network to which the refrigeration system 5 is connected. The first temperature value can then correspond to the temperature of the water supplied by the distribution network.

[0058] Once introduced into the tank 12, the pressure of the liquid water 14 decreases from the initial pressure value to the pressure in the first low-pressure chamber 10, which is at a second pressure value. This corresponds to the transition from point A to point B. During operation, the second pressure value is equal to the saturated vapor pressure of the liquid water 14 present in the tank 12. In one embodiment, the second pressure value in the first low-pressure chamber 10 is typically between 600 Pa (6 mbar) and 2500 Pa (25 mbar), preferably between 600 Pa (6 mbar) and 1500 Pa (15 mbar). As an example, for water at 5 °C, the pressure in the first low-pressure chamber 10 can be 870 Pa (8.7 mbar). The temperature of the liquid water introduced into the tank 12 during the pressure drop remains substantially constant and equal to the first temperature value.

[0059] The temperature of the liquid water 14 in the tank 12 is at a second temperature value. At the start of operation of the refrigeration system 10, the second temperature value is substantially equal to the first temperature value, so that the temperature of the water introduced into the tank 12, whose pressure has decreased, does not change substantially.

[0060] Evaporation occurs of some of the liquid water 14 in the reservoir 12, which will raise the water temperature from the first value to the second value. This corresponds to the transition from point B to point C. Since the pressure in the low-pressure chamber 10 is equal to the saturated vapor pressure of the water at the second temperature value, the vaporization is a boiling of the liquid water 14, which notably includes the formation of bubbles 43 (see figure 1) in liquid water 14. Water vapor is then obtained in the first low-pressure chamber 10 at the second temperature and pressure value. The protective element 20 prevents liquid water from splashing onto the compressor 32 or from spilling out of the tank 12 when the liquid water 14 boils. The protective element 12 can also increase the heat exchange surface area by including parts that penetrate the liquid water.

[0061] In one embodiment, all or part of the water vapor in the first low-pressure chamber 10 is heated by the heating device 22. The temperature of a portion of the water vapor in the first low-pressure chamber 10 then changes from the second temperature value to a third temperature value. In another embodiment, the water vapor is pumped by the compressor 32 into the portion of the first chamber 10 where it is heated. This corresponds to the transition from point C to point D. In one embodiment, the third temperature value is greater than or equal to 0 °C and less than or equal to 100 °C. Preferably, the third temperature value is at least 2 °C higher than the second temperature value, preferably at least 10 °C higher, and more preferably at least 20 °C higher.The water vapor pressure during the heating stage does not vary significantly and remains essentially equal to the second pressure value. The use of the radiant heating device 22 makes it possible to heat all the water vapor that feeds the compressor 32. Indeed, it would be difficult with a conduction or convection heating device to heat all the water vapor that feeds the compressor 32 due to the low pressure and consequently the insufficient density of matter in the first low-pressure chamber 10.

[0062] The steam heated to the third temperature value feeds the compressor 32, which discharges the compressed steam into the second chamber 30 at low pressure. This corresponds to the transition from point D to point E. In one embodiment, the compression ratio of the compressor 32 is greater than or equal to 2 and, for example, less than or equal to 14. The pressure in the second chamber 30 at low pressure is equal to a third pressure value that is at least a factor of 2 higher than the second pressure value. For example, the third pressure value is greater than or equal to 600 Pa (6 mbar) and less than or equal to 10,000 Pa (100 mbar), preferably less than or equal to 6,000 Pa (60 mbar). As an example, when the second pressure value is equal to 870 Pa (8.7 mbar) and the compression ratio of compressor 32 is equal to 2, the third pressure value is approximately equal to 1740 Pa (17.4 mbar).The compression of the water vapor by the compressor 32 causes the water vapor to heat up, its temperature rising from the third temperature value to a fourth temperature value, which is higher than the third temperature value.

[0063] The compressed water vapor in the low-pressure chamber 30 is cooled and then liquefied into cooled liquid water by the condenser 34. This corresponds to the transition from point E to point F and the transition from point F to point G. The water pressure during the cooling and liquefaction stages does not change significantly and remains equal to the third pressure value. The water temperature varies from the fourth temperature value to a fifth temperature value strictly lower than the fourth temperature value. For example, for a third pressure value of 1740 Pa (17.4 mbar), the fifth temperature value could be 15.3 °C. The higher the compression ratio, the more readily the water can be condensed at high ambient temperatures, and the faster the condensation can be achieved.

[0064] The liquid water produced by the condenser 34 is discharged from the tank 30 at low pressure through the pipe 38. In the case of a closed cycle, the pipe 38 is connected to the pipe 18 so that the liquid water discharged from the enclosure 30 is returned to the tank 12.

[0065] Condensation causes pumping by vacuum, linked to the difference in specific volume between liquid water and gaseous water (ratio of approximately 1600 to 200000 between the liquid and gaseous phases), which maintains a vacuum level in the chambers 10 and 30. The maintenance of the pressure difference between the low-pressure chamber 30 and the low-pressure chamber 10 is achieved by the processing module 40 which controls for this purpose the heating device 22, the compressor 32, the condenser 34, the system 42 and possibly the primary vacuum pump.

[0066] The primary vacuum pump operates during the start-up of the refrigeration system 5 until the pressure in the first low-pressure chamber 10 reaches the saturated vapor pressure at the first temperature value. The vacuum pump can then be switched off, and the pressure in chamber 10 is maintained by the vacuum generated at the condenser 34 and the mechanical work of the compressor 32. The vacuum pump can also contribute, if necessary, to maintaining the pressure in the first low-pressure chamber 10.

[0067] THE figures 3 And 4 each represent an enthalpy-pressure diagram of the water illustrating the operation of the refrigeration system 5 in steady state respectively for an open cycle and for a closed cycle.

[0068] In steady state, reservoir 12 is filled with liquid water 14. Additional water is supplied via pipe 18 to reservoir 12 to compensate for liquid water losses from reservoir 12, for example continuously or intermittently. In the case of an open cycle, the additional water is located at point A ( figure 3 ). In the case of a closed cycle, the additional liquid water comes from the condensates recovered in enclosure 30 and is therefore located at point G.

[0069] During the evaporation of liquid water 14 from reservoir 12 described previously, the heat required to produce water vapor is extracted from the liquid water 14 since the first low-pressure chamber 10 is thermally insulated from the external environment. This results in the cooling of the liquid water 14 in reservoir 12. This is reflected on the figures 3 And 4by an additional state represented by point B' in the succession of states followed by water circulating in the installation 5. Indeed, when water is introduced into the tank 12 at the first temperature value and the first pressure value for an open cycle (point A in figure 3 ) and the fifth temperature value and third pressure value for a closed cycle (point G in figure 4 ), there is a decrease in the pressure of this water to the second pressure value, corresponding to the transition from point A to point B, and a decrease in the temperature of the water from the first temperature value to the second temperature value, strictly less than the first temperature value, corresponding to the transition from point B to point B'.

[0070] The pressure in the first low-pressure chamber 10 decreases simultaneously with the decrease in the temperature of the liquid water 14 in the tank 12 to remain equal to the saturated vapor pressure at the temperature of the liquid water 14 in the tank 12. The maintenance of the pressure in chamber 10 at the saturated vapor pressure at the temperature of the liquid water 14 in the tank 12 is achieved by the treatment module 40 which controls for this purpose the heating device 22, the compressor 32 and the condenser 34, the system 42 and possibly the primary vacuum pump.

[0071] According to one embodiment, the temperature of the liquid water 14 in the reservoir 12 decreases until it reaches the triple point temperature of water, which, for example, at a pressure of 611 Pa (6.11 mbar) is equal to 0.01 °C. Ice crystals 15 then form in the reservoir 12, corresponding to the transition between points B' and B" on the figures 3And 4In one embodiment, under steady-state conditions, the temperature of the liquid water 14 in the reservoir 12 remains substantially constant and equal to the triple point temperature of pure water, and the pressure in the first low-pressure chamber 10 is substantially equal to the saturated vapor pressure at the triple point temperature of water. In another embodiment, when water mixing means are provided or when suitable additives are added to the water, under steady-state conditions, the temperature of the liquid water 14 in the reservoir 12 remains substantially constant and equal to a temperature lower than the triple point temperature of pure water, and the pressure in the first low-pressure chamber 10 is substantially equal to the saturated vapor pressure of water in equilibrium with the pressure of water in the liquid state at a temperature lower than the triple point temperature of water.The water is then present in the first enclosure 10 at low pressure simultaneously in the gaseous, liquid, and solid states. According to another embodiment, particularly when the refrigeration system is used in an air conditioning system, the temperature of the liquid water 14 in the reservoir 12 decreases to a temperature less than 10°C above the triple point temperature of water, preferably less than 5°C. The water is then present in the first enclosure 10 at low pressure simultaneously in the gaseous and liquid states.

[0072] In summary, the evaporation of a mass Mev of water will contribute to cooling the remaining mass Mliq of water to the second temperature value, then to solidifying a mass Msol of water, possibly zero, which then transforms into ice according to the following relation (1): M ev * L ev = M liq * C p * Δθ + M sol * L sol where Lev is the latent heat of vaporization of water, Cp is the specific heat capacity of liquid water, Δθ is the difference between the first and second temperature values, and Lsol is the latent heat of solidification of water.

[0073] In the case where water in a solid state is produced, at the end of the cycle, we can have a mass of ice Msol according to the following relation (2): M ev * L ev = M sol * C p * Δθ + L sol

[0074] The other water phase transitions are the same as those described previously in relation to the figure 2In particular, the heating step corresponding to the transition between points C and D aims to increase the temperature of the water vapor in the low-pressure chamber 10 by at least 2 °C, preferably by at least 10 °C, and preferably by at least 20 °C. Furthermore, when the temperature of the liquid water 14 in the tank 12 is decreased, the compression ratio of the compressor 32 can be adjusted to maintain substantially the same third pressure value in the second low-pressure chamber 30. For example, when the second pressure value in the first low-pressure chamber 10 is 611 Pa (6.11 mbar), the compression ratio of the compressor 32 is, for instance, 3, and the third pressure value in the second low-pressure chamber 30 is 1830 Pa (18.3 mbar).As an example, the fifth value of the temperature of the liquid water produced by condenser 34 at 1830 Pa (18.3 mbar) is for example equal to 16.05 °C for an ambient temperature of about 6 °C.

[0075] According to one embodiment, the cold power extraction device 24 removes the ice crystals 15 as they form in the reservoir 12. The subsequent use of the ice crystals depends on the intended application.

[0076] For an application involving the production of artificial snow, ice crystals are collected to produce artificial snow. A refrigeration system can be provided to lower the temperature of the collected ice and / or a pumping unit to evaporate residual water, thus cooling and drying the ice. A device for chopping and aerating the produced ice can also be included.

[0077] For an application for air conditioning or refrigeration and for the production of artificial snow, the ice crystals 15 present in the reservoir 12 can play the role of a cold source.

[0078] The condenser 34 is adapted to liquefy the water vapor in the second low-pressure chamber 30 by means of heat exchange between the water vapor in the second low-pressure chamber 30 and a refrigerant. In one embodiment, the refrigerant is the air outside the refrigeration system 5. The condenser 34 may include means for air mixing, for example, the propeller fan 36 as shown in figure 1Air mixing is schematically represented by arrow 44. Alternatively, the condenser 34 may include a Venturi fan or a thermosiphon. In another embodiment, the condenser 34 may include a water-vapor liquid heat exchanger within the enclosure 30 and a liquid-air or liquid-liquid heat exchanger outside the enclosure 30, with the cooling fluid circulating between these two exchangers.

[0079] Advantageously, the condensation of water in enclosure 30 does not require the use of a refrigeration machine.

[0080] The production of liquid water by the condenser 34 can be achieved using ambient air as soon as the ambient air temperature is below the fifth desired temperature value. In the example described above, in which the condenser 34 produces liquid water at 16.05 °C, ambient air can be used as soon as its temperature is below 16 °C, preferably below 6 °C to obtain a temperature difference of at least 10 °C across the heat exchanger.

[0081] The maximum possible ambient air temperature allowing the use of ambient air as a refrigerant by the condenser 34 is determined, in particular, by the compression ratio of the compressor 32. With a compression ratio of 10, a saturated vapor pressure of 6000 Pa (60 mbar) can be achieved in the second low-pressure chamber 30, and a fifth temperature value of 36 °C can be obtained without difficulty as soon as the ambient air temperature is below 30 °C. Preferably, the refrigeration system 5 can be used as soon as the ambient temperature is below 20 °C for artificial snow production and below 35 °C for air conditioning.

[0082] According to one embodiment, the theoretical COP of the refrigeration installation 5 is in the order of 19 to 20.

[0083] Table I below shows, for an application to artificial snow production, and as a function of ambient air temperature, the electrical consumption, expressed in kilowatts per cubic meter of snow produced, of the refrigeration unit 5 (INV) represented in figure 1 , a snow cannon-type installation (AA1), a snow pole-type installation (AA2), a low-pressure evaporation installation (AA3) between 0.01 MPa (100 mbar) and 0.02 MPa (200 mbar) and an installation refrigerator type (AA4). Table I Ambient temperature (°C) INV AA1 AA2 AA3 AA4 -10 1,6 2 1,9 24 40 -5 1,7 3,1 2,5 25,5 41,5 0 1,85 5,4 3 27 43 10 2,3 N / A N / A 28,5 44,5

[0084] The electrical consumption per cubic meter of snow produced by the refrigeration installation 5 (INV) is significantly lower than that of refrigeration installations of the refrigerator type (AA4) and low pressure evaporation between 0.01 MPa (100 mbar) and 0.02 MPa (200 mbar) (AA3).

[0085] In one embodiment, the liquid water supplied by the condenser 34 is not reused. In another embodiment, the water supplied by the condenser 34 is reused to supply the reservoir 12.

[0086] There figure 5 is a partial and schematic view of a more detailed embodiment of the low-pressure tank 10 of the refrigeration system 5 of the figure 1 .

[0087] In one embodiment, the protective element 20 comprises a membrane or screen 46 covering the free surface of the liquid water 14. The membrane or screen 46 is permeable to water vapor and substantially impermeable to liquid water. The protective element 20 may further comprise elements immersed in the liquid water 14, not shown, which regulate the generation of bubbles 43 during the boiling of the liquid water 14.

[0088] According to one embodiment, baffles 48 can be arranged in the part of the enclosure 10 in which the water vapor is heated by the heating device 22. The baffles 48 allow the path of the water vapor to be lengthened to the inlet of the compressor 32 in order to obtain heating of the water vapor to the desired temperature.

[0089] There figure 6 is a partial and schematic cross-sectional view of a more detailed embodiment of the device 24 for recovering water in the solid state of the refrigeration installation 5.

[0090] In the present embodiment, the device 24 is adapted to extract water in a solid state from the reservoir 12. Such an embodiment is particularly suitable in the case where the refrigeration installation 5 is used for the production of artificial snow.

[0091] The device 24 may include a secondary chamber 50 connected to the reservoir 12 by a lower pipe 52 and an upper pipe 54, located above the lower pipe 52. A pump 56 provided on the upper pipe 54 is adapted to circulate the contents of the reservoir 12 to the secondary chamber 50, and a pump 58 provided on the lower pipe 52 is adapted to circulate the contents of the secondary chamber 50 back to the reservoir 12. The pressure in the secondary chamber 50 may be higher than in the reservoir 12, for example, equal to atmospheric pressure, so that there is no boiling in the secondary chamber 50. The ice crystals then accumulate above the liquid water 62 by settling into a floating mass of ice 60. The device 24 includes means 64 for extracting the ice crystals 60, including, for example, a screw conveyor or a bucket elevator.

[0092] There figure 7is a partial, schematic cross-sectional view of another, more detailed embodiment of device 24. Device 24 may be part of an air conditioning or refrigeration system and may include a closed circuit in which a refrigerant circulates and comprising a first heat exchanger 66 disposed in the reservoir 12 and a second heat exchanger 68 located outside the enclosure 10. According to another embodiment, the first heat exchanger 66 is not present and the liquid circulating in the heat exchanger 68 corresponds to the liquid water 14 present in the reservoir 12.

[0093] There figure 8 is a partial, schematic cross-sectional view of an embodiment of a refrigeration system 70. The refrigeration system 70 comprises all the elements of the refrigeration system 5 shown in figure 1The difference is that it further includes means according to the invention for maintaining the liquid water in a supercooled state within the first chamber 10 at low pressure. In one embodiment, the means for maintaining the liquid water in a supercooled state may include an agitator 72 adapted to stir the water in the liquid state within the first chamber 10 at low pressure. The agitator 72 comprises, for example, a bar or a propeller rotated within the liquid water 14. According to the invention, the means for maintaining the liquid water in a supercooled state include at least one additive added to the water in the liquid state. This additive, when mixed with the water, results in a solution whose freezing point is lower than the freezing point of water without the additive.

[0094] In this embodiment, the temperature of the liquid water 14 in the first low-pressure chamber 10 may be lower than the triple point temperature of water, and is, for example, at a temperature that can vary from -40 °C to -1 °C, preferably from -20 °C to -1 °C. The operation of the refrigeration system 70 is identical to the operation described previously for the refrigeration system 5, except that the temperature of the liquid water in the first low-pressure chamber 10 may be lower than the triple point temperature of water.

[0095] There figure 9 is a partial, schematic cross-sectional view of a more detailed embodiment of part of the refrigeration system of the figure 8 , in which the cold power extraction device 24 in the tank 12 has the structure shown in figure 7The second heat exchanger 68 of the device 24 is located in a container 80 containing liquid water 82 and cools the liquid water 82 until solid water 84 is obtained in the container 80. The pressure in the container 80 may advantageously be greater than the saturated vapor pressure of water at the triple point temperature of water, and be, for example, at atmospheric pressure. In another embodiment, the first heat exchanger 66 is not present, and the liquid circulating in the heat exchanger 68 corresponds to the liquid water 14 present in the reservoir 12.

[0096] There Figure 10 is a partial, schematic cross-sectional view of one embodiment of a refrigeration system 90. The refrigeration system 90 comprises all the elements of the refrigeration system 5 shown in figure 1The difference is that the single tank 12 of the refrigeration system 5 is replaced by N tanks 121 to 12N located in the first low-pressure chamber 10, where N is an integer from 1 to 100. The water supply line 18 is connected to each tank 121 to 12N. Using several tanks 121 to 12N makes it easy to increase the liquid / vapor interface surface area for the same volume of liquid water compared to a single tank. Furthermore, the agitation of the liquid water, particularly by bubbling, is more efficient when the liquid water level is reduced. In this embodiment, the heating device 22 is shown as an example inside the compressor inlet line 32, which opens into the first low-pressure chamber 10.

[0097] In this embodiment, the liquid water recovery line 38 from the condenser 34 is connected to the line 18, and the liquid water recovered by the line 38 is pumped into the tanks 12N to 12N by means of a pump 92, for example, a positive displacement pump. According to another embodiment, the pump 92 may be omitted, the circulation of liquid water in the lines 18 and 38 then resulting solely from the pressure difference between the chambers 10 and 30.

[0098] In the present embodiment, the condenser 34 includes nozzles 94 for projecting liquid water into the second chamber 30 at low pressure in the form of droplets 96, three nozzles 94 being shown by way of example in Figure 10The cold droplets 96 promote the condensation of the water vapor expelled into the second low-pressure chamber 30 by the compressor 32, by multiplying the vapor / liquid interfaces that facilitate the adsorption of water vapor. The liquid water is collected in a reservoir 98, formed, for example, by the bottom of the second low-pressure chamber 30. The line 38 recovers some of the liquid water present in the reservoir 98. The condenser 34 also includes a hydraulic circuit 100 through which some of the liquid water from the reservoir 98 circulates, supplying the nozzles 94 with cooled water.The hydraulic circuit 100 includes a pump 102 for circulating the liquid water and a heat exchanger 104 located outside the second low-pressure enclosure 30, for example, a heat exchanger cooled by ambient air. The condenser 34 includes means, for example, the fan 36 described previously, for circulating ambient air through the heat exchanger 104. Alternatively, the heat exchanger 104 can be cooled by another source, for example, a stream. The liquid water expelled from the nozzles 94, which has been cooled by the heat exchanger 104, is, for example, at ambient temperature. In one embodiment, the temperature of the droplets 96 at the outlet of the nozzles 94 is at least 10 °C lower than the temperature of the liquid water supplying the hydraulic circuit 100.

[0099] In this embodiment, the pressure differential control system 42 between the second low-pressure chamber 30 and the first low-pressure chamber 10 comprises a conduit 106 connected to the second low-pressure chamber 30 in the portion of the chamber 30 containing steam. The conduit 106 is equipped with a flow-controllable valve 108 and supplies an expansion turbine 110. The outlet of the turbine 110 is connected to a conduit 112 that supplies each reservoir 12N. The turbine 110 receives steam at the pressure of the second low-pressure chamber 30, which is already cooled by the droplet condenser 34, and provides a two-phase mixture comprising liquid water and steam. The rotational speed of the turbine 110 is adjusted so that the discharged steam has the desired pressure.According to one embodiment, in the two-phase mixture exiting turbine 110, the liquid water has been cooled by expansion, and the steam is substantially at the desired pressure in the first low-pressure chamber 10. The steam expelled through line 112 into each tank 12N can advantageously act as an agitator for the liquid water present in tanks 12N and further promotes the cooling of the liquid water contained in tanks 12N. Turbine 110 and valve 108 can be controlled by the treatment module 40, not shown in Figure 1. Figure 10 .

[0100] In this embodiment, the cold power extraction device 24 in the tanks 121 to 12N comprises a hydraulic circuit 114 connected to the tanks 121 to 12N through which some of the water present in the tanks 121 to 12N circulates. The hydraulic circuit 114 includes a pump 116 for circulating the liquid water and a heat exchanger 118 located outside the first low-pressure enclosure 10, for example, a heat exchanger cooperating with a heat exchanger 120 of another hydraulic circuit 122 connected to a device 124 to be cooled. As shown in Figure 10 , the hydraulic circuit 114 can be connected to the pipe 18 for the discharge of the liquid water circulating in the hydraulic circuit 114 to the tanks 12 1 to 12 N.

[0101] According to the invention, the turbocharger 32 comprises two successive stages 130 and 132. The first stage 130 has a fixed compression ratio, for example, approximately 3, and the second stage 132 has a controllable variable compression ratio. The rotational speed of the second turbomachine 132 can be controlled by the processing module 40, not shown in the figure. Figure 10 Preferably, each stage 130, 132 corresponds to a turbocharger. The first stage 130 controls the flow rate of steam extracted from the first chamber 10 at low pressure. The second stage 132 sets the pressure of the steam discharged into the second chamber 30 at low pressure.

[0102] In Figure 10 In addition, a primary vacuum pump 134 connected to the first low-pressure chamber 10 via a pipe 136 equipped with a controllable valve 138 has been shown.

[0103] Specific embodiments have been described. Various variants and modifications will be apparent to those skilled in the art. In particular, although in the embodiments described above, the condenser 34 is a condenser in which the water vapor is cooled and liquefied by the ambient air, other types of condenser 34 may be used, for example, a liquid-cooled condenser.

Claims

1. A refrigeration plant (5; 70) comprising: a first enclosure (10) containing water in the liquid state (14) at a temperature lower than the triple point temperature of water, water in the gaseous state (11) at a first pressure equal, to within 10%, to the saturation vapor pressure of the water in equilibrium with the pressure of the water in the liquid state (14) in the first enclosure, and water in the solid state (15) at a temperature lower than the triple point temperature of water, the first enclosure (10) comprising at least one reservoir (12; 121 to 12N) of water in the liquid state; means for maintaining the liquid water in a supercooled state in the first enclosure (10), said means comprising at least one additive added to the water in the liquid state; a second enclosure (30) at a second pressure strictly higher than the first pressure by at least a factor of two; a compression device (32) connecting the first enclosure to the second enclosure, adapted to provide a compression ratio greater than two; a condensation device (34) partially housed in the second enclosure and adapted to condense the water in the gaseous state in the second enclosure into water in the liquid state; and a device (24) for extracting cooling power in the first enclosure; the refrigeration plant being characterized in that it comprises a rough vacuum pump, connected to the first enclosure (10) and / or to the second enclosure (30) and in that the compression device (32) comprises two successive stages (130, 132), each stage (130, 132) corresponding to a turbocharger, with a first compressor stage (130) having a fixed compression ratio and a second compressor stage (132) having a controllable compression ratio, the rotation speed of the second turbocharger being controlled by a processing module (40).

2. The refrigeration plant according to claim 1, wherein the first stage (130) controls the flow rate of water vapor extracted from the first enclosure (10) and the second stage (132) sets the pressure of the water vapor discharged into the second enclosure (30).

3. The refrigeration plant according to any of claims 1 or 2, wherein the temperature of the liquid water (14) in the reservoir (12; 121 to 12N) remains substantially constant and equal to a temperature lower than the triple point temperature of pure water and wherein the pressure of the first enclosure (10) is substantially equal to the saturation vapor pressure of the water in equilibrium with the pressure of the water in the liquid state at the temperature lower than the triple point temperature of water.

4. The refrigeration plant according to any of claims 1 or 2, wherein the temperature of the liquid water (14) in the reservoir (12; 121 to 12N) is greater than or equal to the triple point temperature of pure water.

5. The plant according to any one of claims 1 to 4, further comprising a system (42) for regulating the pressure difference between the second enclosure (30) and the first enclosure (10), comprising an expansion turbine (110) configured to expand water in the gaseous state from the second enclosure (30) and discharge a mixture containing water in the gaseous state and water in the liquid state into the first enclosure (10), said mixture being discharged into the water in the liquid state contained in said reservoir.

6. The refrigeration plant according to any of claims 1 to 5, comprising a device (22) for heating water in the gaseous state in the first enclosure (10) intended to supply the compression device (32), the heating device (22) comprising a source of microwave radiation and / or a source of infrared radiation.

7. The plant according to any one of claims 1 to 6, wherein the water circulates in a closed circuit within the plant.

8. The refrigeration plant according to any one of claims 1 to 7, wherein the condensation device (34) comprises a first heat exchanger outside the second enclosure (30) and means (36) for circulating a first heat transfer fluid through the first heat exchanger, the first heat transfer fluid preferably being ambient air or water from a stream, a body of water and / or a ground water.

9. The refrigeration plant according to any one of claims 1 to 8, wherein: the cooling power extraction device (24) comprises a hydraulic circuit in which some or all of the water in the liquid state present in the first enclosure (10) circulates, the hydraulic circuit comprising a second heat exchanger (68) located outside the first enclosure; or the cooling power extraction device (24) comprises a closed hydraulic circuit in which a second heat transfer fluid circulates, the hydraulic circuit comprising a second heat exchanger (68) located outside the first enclosure and a third heat exchanger (66) arranged in the first enclosure (10).

10. The refrigeration plant according to any one of claims 1 to 9, comprising, in the first enclosure, a device (20) for protecting the compression device (32) against the admission of particles in the solid and / or liquid state.

11. The plant according to any one of claims 1 to 10, wherein the condensation device (34) comprises at least one nozzle (94) for spraying droplets (96) of water in the liquid state into the second enclosure (30).

12. An air conditioning system, intended for industrial plants, comprising a refrigeration plant according to any one of claims 1 to 11.

13. An artificial snowmaking system comprising a refrigeration plant (5) according to any one of claims 1 to 11.

14. A method for generating cold comprising the following steps: bringing water in the liquid state (14) into a first enclosure (10) at a temperature lower than the triple point temperature of water, forming water in the gaseous state at a first pressure equal, to within 10%, to the saturation vapor pressure of water in equilibrium with the pressure of the water in the liquid state in the first enclosure, maintaining the liquid water in a supercooled state in the first enclosure (10) by means comprising at least one additive added to the water in the liquid state, and forming water in the solid state (15) at a temperature lower than the triple point temperature of water; compressing water in the gaseous state from the first enclosure to a second enclosure at a second pressure strictly higher than the first pressure by at least a factor of two, by a compression device (32) comprising two successive stages (130, 132), each stage (130, 132) corresponding to a turbocharger, with a first compressor stage (130) having a fixed compression ratio and a second compressor stage (132) having a controllable compression ratio, the rotation speed of the second turbocharger being controlled by a processing module (40); condensing the water in the gaseous state in the second enclosure into water in the liquid state; and extracting cooling power in the first enclosure.