OA20234A - Refrigeration plant. - Google Patents

Abstract

This refrigeration installation comprises a very low temperature (TB) module comprising a first circuit conveying a first refrigerant, comprising a first compressor (3, 71), a first heat exchanger (5), a first expansion valve (7, 52), a first pump (11, 51) and a first evaporator (13, 54), characterized in that the first refrigerant fluid is a liquid/vapor phase change fluid, and in that this installation comprises a reservoir (9, 70 ) whose lower part communicates with said first expander (52) and with said first pump (11, 51), and whose upper part communicates with said first evaporator (13, 54) and said first compressor (3, 71). Figures for the abstract:

Description

DESCRIPTION

TITLE: REFRIGERATION PLANT

The present invention relates to a refrigeration installation, in particular for foodstuffs.

Stand-alone refrigeration installations are known from the prior art, that is to say not connected to the mains electric current.

Such installations, connected for example to photovoltaic panels, use the electric current produced by these panels to operate a conventional refrigeration circuit, comprising a condenser placed outside the enclosure to be cooled, and an evaporator placed outside the enclosure. inside this enclosure.

During nighttime operation, i.e. when the photovoltaic panels no longer produce electricity, there are different solutions for continuing to produce cold.

A first solution consists in recharging electric accumulators during the day by means of the current produced by the photovoltaic panels, these accumulators restoring during the night the electric current necessary for the operation of the refrigeration installation. This first solution requires the use of high-capacity accumulators with a limited lifetime, which leads to high costs.

A second solution consists in using ice, produced by the refrigeration installation during the day, and the melting of which during the night provides the cold temperatures necessary to maintain low temperatures in the refrigerated enclosure. This second solution has the disadvantage of not making it possible to reach very low temperatures, and of not making it possible to control or regulate the amount of thermal reserve available.

Thus, the present invention aims to provide a refrigeration installation making it possible to reach very low temperatures, without however using high-capacity accumulators and whose available thermal reserve can be perfectly known and regulated.

This object of the invention is achieved with a refrigeration installation comprising a very low temperature module comprising a first circuit conveying a first refrigerant, comprising a first compressor, a first heat exchanger, a first expansion valve, a first pump and a first evaporator , remarkable in that the first refrigerant is a fluid with liquid/vapor phase change, and in that this installation comprises a tank whose lower part communicates with said first pressure reducer and with said first pump, and whose upper part communicates with said first evaporator and said first compressor.

The use of a reservoir containing a coolant with liquid/vapor phase change makes it possible, in an extremely simple and perfectly controllable way, to enrich the liquid phase of this reservoir in daytime operation when the compressor is operating, then, by simple pumping and evaporation of the liquid phase towards the gaseous phase of the cooling fluid located in the tank, to cool with very low energy consumption the products located in the refrigerated enclosure, in night mode.

This low energy can be provided by low capacity accumulators.

According to other optional features of the first embodiment of the present invention:

- it further comprises a low temperature module connected in cascade to said first heat exchanger;

- said low temperature module comprises a second cooling circuit comprising a cold source formed by a solid/liquid phase change material, and a third cooling circuit comprising means for cooling this material;

- the second cooling circuit comprises a unit for storing said solid/liquid phase change material, and it conveys a second cooling fluid circulating in a second pump, in a second heat exchanger, in a third heat exchanger, and in said first heat exchanger, then returning to said storage unit; - said third cooling circuit conveys a third cooling fluid circulating in a second compressor disposed downstream of the second heat exchanger, in a condenser, in a second expansion valve, then returning to said second heat exchanger;

- Said third cooling fluid may be a synthetic cooling fluid of the hydrofluoro-carbon olefin type; of the hydro-fluoro-olefin type, of the hydro-fluoro-carbon type or carbon dioxide of the R744 type;

- Said first cooling fluid can be carbon dioxide of the R744 type, of synthetic type of hydro-fluoro-carbons or of the hydro-fluoro-olefins type.

The use of carbon dioxide of the R744 type is particularly suitable as a liquid/vapor phase change cooling fluid, given that it is both very easily pumpable and not very dangerous for the environment.

According to other optional features of the second embodiment of the present invention:

- the very low temperature module comprises a condenser, the first heat exchanger and the condenser being arranged in the same storage unit;

- the very low temperature module comprises a tank configured to act as a liquid/vapor separator connected on the one hand to the tank and on the other hand to the storage unit and a low pressure vapor/liquid bottle, the tank being configured to conveying said fluid from a pump configured to circulate the fluid from the vapor/liquid low pressure cylinder to said storage unit, via the evaporator, to the vapor/liquid separator, said reservoir (70) being configured to have the function of an expansion vessel in night mode;

- it further comprises a low temperature module connected in cascade or by direct discharge, on the one hand to said first compressor by a first connection and on the other hand to said low pressure vapour/liquid bottle by a second connection;

- that a second compressor is included and connected by pipes, on the one hand to the separator and on the other hand to the first connection;

- Said first cooling fluid may be carbon dioxide of the R744 type, a synthetic cooling fluid of the hydro-fluoro-carbon type or of the hydro-fluoro-olefin type. Other characteristics and advantages of the present invention will appear in the light of the description which follows, and on examination of the appended figure, representing an installation according to the present invention, in the particular case where it comprises on the one hand a very low temperature cooling circuit, and on the other hand a low temperature cooling circuit mounted in cascade with the previous one.

It should however be clearly understood that the invention is not limited to this complex installation, and that it relates more particularly to the very low temperature cooling circuit, which could be used independently of the low temperature cooling circuit.

In the description below, the tank configured to act as a liquid/vapor separator is referred to as a “separator”.

[Fig. 1] represents a diagram of a refrigeration installation according to a first embodiment of the invention.

[Fig. 2] represents a diagram of a refrigeration installation according to a second embodiment of the invention.

Referring to the appended Figure 1, it can be seen that the very low temperature circuit, designated by the general reference TB, comprises pipes 1 conveying a first cooling fluid, these pipes interconnecting a first compressor 3 supplied by a source electrical energy, a first heat exchanger 5, a first expansion valve 7, a tank 9, a first pump 11 and an evaporator 13 located in an enclosure where it is desired to maintain products, such as foodstuffs, at a temperature very low core, typically within a range of -20°C to -40°C.

More precisely, the tank 9 is connected in its lower part on the one hand to the first regulator 7, and on the other hand to the first pump 11, and in its upper part on the one hand to the evaporator 13 and to the first compressor 3.

Lines 1 and reservoir 9 contain a pumpable liquid/vapor phase change coolant, such as carbon dioxide R744.

Thus, in the lower part of the tank 9 is the liquid phase of this fluid, and in the upper part of this tank is the vapor phase of this liquid.

The low temperature cooling circuit, designated by the general reference B in the appended figure, firstly comprises a unit 15 for storing a solid/liquid phase change cooling material.

Such a material, known per se, may be a water-insoluble organic phase change material derived from plant-based raw materials and in the form of a crystalline wax or an oily liquid, non-corrosive and nontoxic.

Typically, this phase change material liquefies at around -21°C, and crystallizes at 27°C.

The storage unit 15 is connected by pipes 17 to a second pump 19, to a second heat exchanger 21, to a third heat exchanger 23 located in an enclosure, separate from the previous one, in which there are products that the it is desired to maintain a core temperature typically located within a range of -5°C to +10°C.

The third heat exchanger 23 is itself connected to the first heat exchanger 5, which in turn is connected to the storage unit 15.

In the pipes 17 circulates a second cooling fluid.

The second heat exchanger 21 is connected by pipes 25 successively to a second compressor 27, to a condenser 28, to a fluid storage tank 29, and to a second pressure reducer 31 itself connected to this second heat exchanger 21.

A third cooling fluid, such as a synthetic fluid of the hydro-fluoro-carbon olefin type, of the hydro-fluoro-carbon type or carbon dioxide R744, circulates in the pipes 25.

The mode of operation of the refrigeration installation described above is as follows.

During the day, electric current which may come from photovoltaic panels, or from any other current generator not connected to the mains (for example electrical energy of wind origin) supplies the compressors 3 and 27, as well as the pumps 11 and 19.

The first compressor 3 makes it possible to compress the vapor phase of the first cooling fluid located in the upper part of the tank 9.

The heat given off by this compression is evacuated via the first heat exchanger 5 into the second cooling fluid circulating in the pipes 17 of the low temperature module.

During its expansion through the expansion valve 7, the first cooling fluid sees its temperature drop considerably, and its pumping by the pump 11 in the direction of the evaporator 13 makes it possible to cool the products located in the enclosure to very low temperature.

In doing so, this evaporation also has the effect of enriching the vapor phase located inside the tank 9.

The cascade cooling of the first cooling fluid circulating in the pipes 1 by the second cooling fluid circulating in the pipes 17, is operated via the first heat exchanger 5.

In daytime operation, the second cooling fluid, the circulation of which is ensured by the second pump 19, is cooled by the third cooling fluid circulating in the pipes 25, itself undergoing a compression/expansion cycle thanks to the second compressor 27 and to the second regulator 31.

More precisely, this third cooling fluid makes it possible, via the second heat exchanger 21, to sufficiently lower the temperature of the second cooling fluid circulating in the pipes 17, to ensure, during the day, the crystallization of the change material. solid / liquid phase located in the storage unit 15, and whose crystallization temperature can typically be of the order of -27 ° C.

The second cooling liquid circulating in the pipes 17 makes it possible, thanks to a third heat exchanger 23, to ensure a low temperature in an enclosure where there are products whose core temperature is to be maintained within a range which can typically range from - 5°C to +10°C.

During the night, the external source of electrical supply (for example photovoltaic panels) no longer produces electricity, and compressors 3 and 27 cease to operate. Only the pumps 11 and 19 operate, on accumulators of relatively low capacity.

The operation of the pump 11, making it possible to circulate the first cooling fluid through the evaporator 13, gradually converts the liquid phase of this fluid located in the tank 9 into the gaseous phase located in the upper part of this tank, supplying on the way the cold temperatures necessary to maintain the products located in the enclosure concerned at a very low temperature.

With regard to the low temperature enclosure, the desired low temperature is maintained thanks to the circulation of the second cooling fluid in the pipes 17 by means of the second pump 19, this second fluid being cooled by the melting of the change material phase located inside unit 15.

Figure 2 shows a refrigeration installation according to a second embodiment of the invention.

It can be seen that the very low temperature circuit TB comprises elements interconnected by pipes 1. The pipes 1 are configured to convey a first cooling fluid from a low pressure vapour/liquid bottle 50 by pumping the double pumps 51 refrigerant.

The low-pressure bottle 50 comprises a pressure reducer, here a valve 52, which can be electronic, as well as a sensor 53 of the level of the liquid contained in the bottle 50.

The pumped fluid is then directed to evaporators 54 mounted in parallel allowing the air in the cold rooms of each evaporator 54 to be cooled to a given temperature T, the air being blown by fans 55.

Each evaporator outlet extends into a single pipe 1 at a junction point 56 in order to connect to a storage unit 57 having several functions such as that of an evaporator, a condenser or a tank at latent heat.

In parallel, a pipe 1 directly connects the double pumps 51 to the storage unit 57. Between each element of the installation connected by the pipes 1 is integrated at least one electromagnetic valve 52, the opening and/or closing of each valve 52 being controllable, for example on command or by temperature sensor.

A vapour/liquid separator 60 is connected by a pipe 1 to the storage unit 57. In parallel, another pipe 1 directly connects the pipe 1 joining each evaporator outlet 54 to the separator 60.

The separator 60 is also directly connected to the low pressure vapour/liquid bottle 50 by a pipe 1.

The separator 60 further comprises a liquid level sensor making it possible to control the corresponding valve 52, here referenced 52a.

The separator 60 is itself connected to a reservoir 70. This reservoir 70 is a vapor bottle called an expansion vessel. Indeed, the reservoir 70 has the function of an expansion vessel in night mode and in particular by preventing a rise under pressure in the evaporator 54, the separator 60 and the low pressure bottle 50 when the fluid has cooled. Reservoir 70 is connected to a first compressor 71.

A low temperature module B is connected in cascade or direct discharge, on the one hand to the first compressor 71 by a first connection 72 and on the other hand to said vapor/liquid low pressure cylinder 50 by a second connection 73.

In addition, a second compressor 74 is included and connected by pipes 1, on the one hand to the separator 60 and on the other hand to the first connection 72. The low temperature module B comprises an air condenser 80 connected to a vertical tank 81 .

In the following paragraphs, the operation of the invention according to the second embodiment is explained.

In daytime mode, electric current which may come for example from photovoltaic panels, or indeed from any other current generator not connected to a mains, for example electrical energy of wind origin, supplies the compressors 71, 74 and the condenser at air 80 as well as the double pumps 51 and the fans 55 of the evaporators 54.

During its expansion through the expansion valve, here a valve 52 arranged at the level of the low pressure vapor / liquid bottle 50, the refrigerant sees its temperature T drop considerably, and its pumping by the double pumps 51 in the direction of the The evaporator 54 makes it possible to cool the products located in the enclosure at very low temperature TB.

The operation of the double pumps 51, making it possible to circulate the refrigerant through the evaporator 54, gradually converts the liquid phase of this fluid located in the low vapor/liquid pressure bottle 50 into the gaseous phase, supplying on the way the cold necessary to maintain the products located in the enclosure concerned at a very low temperature.

In doing so, this evaporation also has the effect of enriching the vapor phase at the outlet junction point 56 of each evaporator 54.

In night mode, the valve 52 arranged between the outlet junction point 56 of each evaporator 54 is open, the valve 52 arranged at the level of the pipe 1 directly connecting the outlet junction point 56 of each evaporator 54 to the separator 60 is closed. closed and this enriched vapor phase passes through the storage unit 57 and partially condenses by melting the PCM (Phase Change Material) which gives up its latent heat to the vapor which condenses.

In night mode, the vapor and liquid phases coming from the evaporators 54 and from the storage unit 57 by the above-mentioned pipe paths 1, are separated by the separator 60 and the excess pressure is absorbed by the tank 70 having been brought back at a pressure PI lower than a saturation pressure P2 equivalent to temperature T in daytime mode.

In daytime mode, the valves 52 arranged respectively at the level of the pipe 1 directly connecting the outlet junction point 56 of each evaporator 54 to the separator 60 and at the level of the pipe 1 directly connecting the double pumps 51 to the storage unit 57 are open, the valve 52 connecting the outlet junction point 56 of each evaporator 54 to the storage unit 57 is closed. The twin pumps 51 always pass the liquid through the evaporators 54 and via the valve 52, directly connecting the twin pumps 51 to the storage unit 57, opened through the storage unit 57. The evaporation of the liquid refrigerant through the storage unit 57 solidifies the PCM.

In daytime mode, at the level of the pipe 1 connecting the separator 60 to the storage unit 57 and the separator 60 to the junction point 56 at the outlet of each evaporator 54, the vapor and liquid phases coming from the evaporators 54 and from the storage unit 57 are separated by the separator 60 and the excess vapor is sucked up by the second compressor 74 while the excess liquid is evacuated via the valve 52 arranged at the level of the pipe 1 directly connecting the low pressure vapor cylinder / liquid 50 to the separator 60, to the low pressure vapor / liquid bottle 50, the valve 52 being controlled by the liquid level sensor.

During the night, the external source of electrical supply, for example the photovoltaic panels, no longer produces electricity, and the first and second compressors 71 and 74 cease to operate. Only the double pumps 51 and the fans 55 of the evaporators 54 operate, on accumulators of relatively low capacity.

In daytime mode, at full electrical load by the photovoltaic panels for example, or other intermittent sources, the second compressor 74 makes it possible to solidify the molten PCM in phase and the first compressor 71 makes it possible to lower the pressure of the reservoir 70 to the value equivalent saturation pressure PI at temperature T-30°C. In all cases, the PI pressure will be greater than 1 bar and the triple point of the fluid used.

Depending on the system on which this intermittent stage is grafted, an additional low temperature circuit B for refrigeration production may prove necessary, the operation of which will be slaved to the first and second compressors 71 and 74, therefore in daytime mode only.

As can be understood in the light of the preceding description, the refrigeration installation according to the invention, which can be used either only with the very low temperature module, or with a combination of this module with the low temperature module, maintains the desired low temperatures when the installation is no longer supplied with electrical current.

This invention is therefore particularly suitable for refrigeration installations powered by autonomous and intermittent electrical sources, such as photovoltaic panels, or even wind turbines.

An installation according to the invention can thus be installed in very remote areas, not connected to the mains electric current.

Electronic regulation can advantageously be envisaged, in order to control the charges and discharges of cold storage stored in connection with the charge available in the electric accumulators in night mode and the peak current available in daytime mode.

In a particularly advantageous manner, the refrigeration installation according to the embodiments of the invention can be mobile, and comprise 2 enclosures, one of which is very low temperature with the aim of obtaining a core temperature of the refrigerated products situated between - 20°C and -40°C, and the other low temperature with the aim of obtaining a core temperature of refrigerated products between -5°C and +10°C.

Of course, the present invention is in no way limited to the embodiments described and represented.

Other phase change fluids and materials than those mentioned can be used. For example, the refrigerant R404A (zeotropic mixture of fluorethanes) can be an alternative to carbon dioxide R744.

Claims (16)

1. Refrigeration installation comprising a very low temperature (TB) module comprising a first circuit conveying a first refrigerant, comprising a first compressor (3), a first heat exchanger (5), a first expansion valve (7), a first pump (11) and a first evaporator (13), characterized in that the first refrigerant fluid is a liquid/vapor phase change fluid, and in that this installation comprises a tank (9) whose lower part communicates with the said first expander (7) and with said first pump (11), and whose upper part communicates with said first evaporator (13) and said first compressor (3). 2. Installation according to claim 1, characterized in that it further comprises a low temperature module (B) connected in cascade to said first heat exchanger (5). 3. Installation according to claim 2, characterized in that said low temperature module (B) comprises a second cooling circuit comprising a cold source (15) formed by a solid/liquid phase change material, and a third cooling circuit. cooling comprising means for cooling this material. 4. Installation according to claim 3, characterized in that the second cooling circuit comprises a storage unit (15) of said solid/liquid phase change material, and in that it conveys a second cooling fluid circulating in a second pump (19), in a second heat exchanger (21), in a third heat exchanger (23), and in said first heat exchanger (5), then returning to said storage unit (15). 5. Installation according to one of claims 3 or 4, characterized in that said third cooling circuit conveys a third cooling fluid circulating in a second compressor (27) disposed downstream of the second heat exchanger (21), in a condenser (28), in a second expansion valve (31), then returning to said second heat exchanger (21). 6. Installation according to claim 5, characterized in that said third cooling fluid may be a synthetic cooling fluid of the hydro-fluoro-carbon olefin type; of the hydro-fluoro-olefin type, of the hydro-fluoro-carbon type or carbon dioxide of the R744 type. 7. Refrigeration installation comprising a very low temperature (TB) module comprising a first circuit conveying a first liquid/vapor phase-change refrigerant, the first circuit comprising: - a low pressure vapour/liquid bottle (50), - an evaporator (54), - a storage unit (57), - a first reservoir (60) configured to act as a liquid/vapor separator, and - a second tank (70) configured to act as an expansion vessel in night mode, - a valve (52) configured to circulate said first fluid from the vapor/liquid low pressure bottle (50) to said storage unit (57) via the evaporator (54), the first tank (60) being connected , on the one hand, to the second tank (70) and, on the other hand, to the storage unit (57) and to the low pressure vapour/liquid bottle (50). 8. Refrigeration installation according to the preceding claim, characterized in that it comprises a compressor (71) connected to the second tank (70). 9. Refrigeration installation according to the preceding claim, characterized in that it further comprises a low temperature module (B) connected in cascade or in direct discharge, on the one hand to said compressor (71) by a first connection (72) and on the other hand to said low pressure vapour/liquid bottle (50) via a second connection (73). 10. Installation according to the preceding claim, characterized in that it comprises a second compressor (74) connected, on the one hand, to the separator (60) and, on the other hand, to the first connection (72). 11. Refrigeration installation according to any one of claims 7 to 10, characterized in that: - in night mode, refrigeration is provided by the very low temperature module (TB), - in daytime mode, refrigeration is provided by the low temperature module (B). 12. Refrigeration installation according to any one of claims 7 to 11, characterized in that the storage unit (57) comprises a phase change material (PCM), and in that: - in night mode, the storage unit (57) operates as a condenser to liquefy the phase change material (PCM), - in daytime mode, the storage unit (57) operates as an evaporator to solidify the phase change material (PCM). 13. Refrigeration installation according to any one of claims 7 to 12, characterized in that, (i) in daytime mode, the first fluid circulates from the vapor/liquid low-pressure bottle (50) on the one hand towards the evaporator (54), and on the other hand to the storage unit (57) mounted in parallel with the evaporator (54) and (ii) in night mode, the first fluid circulates from the low pressure vapour/liquid bottle ( 50) to the evaporator (54) then to the storage unit (57). 14. Refrigeration installation according to any one of claims 7 to 13, characterized in that it comprises a second evaporator (54), the first evaporator (54) and the second evaporator (54) being mounted in parallel and each connected to said storage unit (57). 15. Refrigeration installation according to any one of claims 7 to 14, characterized in that it comprises double pumps (51) connected to the storage unit (57). 16. Refrigeration installation according to any one of the preceding claims, characterized in that the said first cooling fluid can be carbon dioxide of the R744 type, a synthetic cooling fluid of the hydro-fluoro-carbon type or of the hydro -fluoro-olefins.