COOLING SYSTEM

Description

FIELD OF THE APPLICATION

[0001] The present invention is enclosed in the field of refrigeration systems. More particularly, the present invention relates to industrial and commercial refrigeration systems.PRIOR ART

[0002] Refrigeration is the transfer of heat from an object or space, cold source, at a certain temperature, lower than that of the environment in which it is located, to another at a higher temperature, heat sink, usually the environment, reducing or maintaining the cold source temperature. Since, from a physical point of view, heat is transferred towards lower temperatures, the above phenomenon is possible through the supply of energy in the so-called refrigeration cycles, in which, by evaporation of a working fluid, a refrigeration effect is produced.

[0003] The exchange of heat between the cold source and the heat sink is achieved through the use of a thermal machine, typically called a refrigerating plant or refrigeration system. Such system uses the energy at the input of compressor devices, in order to operate a refrigeration cycle intended to cool and / or heat a given heat exchanger. Over the years, new systems operating with different working fluids have been introduced that aim to increase the efficiency of a refrigeration system.

[0004] In general, there are two defined temperature levels in industrial and commercial refrigeration. The medium evaporation temperature conservation (MT) and the low evaporation temperature conservation (LT). MT is normally carried out at evaporation temperatures corresponding to -20 to 0°C and LT is normally carried out at evaporation temperatures corresponding to -40 to -20°C.

[0005] In traditional refrigeration systems, to reach these temperatures, two different thermal machines normally have to be used, which may or may not operate independently.

[0006] There are, however, systems in which the fluid at evaporation temperatures LT is compressed to an intermediate pressure, the pressure equivalent to the evaporation temperature MT, and is subsequently mixed with a fluid from medium temperature storage and both flows are compressed again, following the normal operation of a refrigeration cycle, in which the fluid is cooled in a heat exchanger (e.g. condenser or gas cooler), expanded and sent to the cold sources of low and medium temperature, thus restarting the refrigeration cycle. These systems are known in the refrigeration industry by booster cycles.

[0007] In most industrial and commercial refrigeration systems, a type of evaporation of the working fluid in the cold source known as dry evaporation, or direct evaporation, is used. In this type of evaporator, the working fluid, mostly in liquid form, is admitted through an expansion valve and is evaporated before being sent to a compressor. The expansion valve is regulated according to the conditions of the fluid leaving the evaporator in order to guarantee considerable superheating and that there is no liquid in the compressor suction lines.

[0008] However, superheating the working fluid leads to a loss of heat exchange efficiency, as the heat transfer coefficient is lower when the fluid is in the vaporized state compared to the liquid state. This means that most of the heat transfer will take place while the fluid is mostly in the liquid state and not when it is already in the vaporized state.

[0009] In an attempt to circumvent this loss of efficiency, flooded evaporators and semi-flooded evaporators have been studied as an alternative to dry evaporators.

[0010] In a flooded-evaporator, the admitted working fluid is not completely evaporated in the heat exchange with the cold source and, consequently, there is no superheating. Given these conditions, the evaporator may be completely filled with liquid, "flooded", resulting in an increase in heat transfer efficiency when compared to dry evaporators. The increased performance of this component allows it to operate at higher evaporation temperatures than dry evaporators, which results in a decrease in compression work. To achieve such increase of performance, a flooded evaporator typically operates in an overfeeding regime, which means that the total flow rate circulating in the evaporator is greater than the evaporated flow rate, usually between 2 and 7 times. Thus, recirculating mechanisms have to be considered in order to circulate the liquid in the tank to the evaporator inlet, returning this to the tank at the outlet where the part of the fluid that evaporates goes to the compressor and the other part, which remains in the liquid state, is recirculated.

[0011] In a semi-flooded evaporator, the superheating is very close to 0 K, which means that its efficiency is comparable to that of the flooded evaporators, even with a lower flow rate, since almost all the fluid is in the liquid state while passing through the evaporator. In order to protect the compressors, a suction accumulator is usually used, which is a tank that may have smaller dimensions than the one used in the flooded evaporators, as the amount of liquid reaching the evaporator outlet is very small. In order to remove the liquid formed in the suction accumulator, systems that use liquid pumps or, more recently, systems that use ejectors, which are more efficient, can be used.

[0012] As such, the introduction of these alternatives to dry evaporators implies an increase in the complexity of an industrial or commercial refrigeration system, in particular with the increase in the number of the system components, and respective technical specifications, and in the associated control logic to guarantee the normal operation of the system at different temperature levels (e.g. LT and MT).

[0013] This extra complexity translates into an increase in the total space occupied by the system and in high installation costs, which has postponed the option for these evaporators in industrial and commercial refrigeration systems. EP 3 798 533 A1 discloses a refrigeration system which comprises two evaporation branches, each of which is configured to operate at a predefined evaporation level, an ejector, a liquid separator and two compressors and a high-pressure branch. The fluidic connections and valve means fluidically connect the first evaporation branch to the expansion device in such a way that the expansion device is fed by the outlet of the first evaporation branch; the expansion device to the liquid separator in such a way that the liquid separator is fed by the outlet of the expansion device; the liquid separator to the second evaporation branch, in such a way that the second evaporation branch is fed by the liquid obtained from the liquid separator. The high-pressure branch is connected to the first evaporation branch in such a way that the first evaporator branch is fed by the high-pressure branch, and wherein, each evaporation branch is configured to operate at a different evaporation level, the first evaporation branch is configured to operate at a medium evaporation level, and the second evaporation branch is configured to operate at a low evaporation level.

[0014] The solution described in the present invention intended to innovatively overcome such issues.SUMMARY OF THE INVENTION

[0015] It is therefore an object of the present invention to provide a refrigeration system, comprised by at least two evaporation branches, each of which configured to operate at a predefined evaporation level, an expansion device and a liquid separator. The system further comprises a plurality of fluidic connections and valve means that are specially configured to connect the above-mention elements to each other, in a particular advantageous way. A refrigeration system according to the present invention is defined in claim 1.

[0016] The system described in the present invention incorporates an alternative to dry evaporators, and is projected to obtain an increase in heat transfer efficiency when compared to traditional refrigeration systems, without this resulting in an increase in the cost of initial investment or maintenance. Additionally, this increase in efficiency results from a simplification in the architecture of the system, that no longer needs certain elements that are essential for current state-of-the-art refrigeration systems, such as recirculation mechanisms used in flooded evaporators to implement overfeeding operation regimes, or additional tanks (the so-called suction accumulator) used in semi-flooded evaporators to protect compressors.

[0017] This efficiency is achieved through a system architecture comprised by a particular set of system elements, fluidic connections and valve means, arranged to achieve a generalized simplification when compared to other systems, which also translates into a reduction in the overall space occupied by the system, making installation, maintenance and control tasks easier.

[0018] The system is also designed to favour its integration with other refrigeration elements that can be previously installed on site, such as evaporators and / or compressors.

[0019] Alternatively, in an advantageous configuration of the system, it is comprised by a plurality of evaporators, the evaporators being fluidically connected to an evaporation branch and being configured to operate at the respective branch's predefined evaporation level.

[0020] In another advantageous embodiment, the system may further comprise at least two compressor branches, each of which comprising at least one compressor.DESCRIPTION OF FIGURES

[0021] Figure 1 - representation of an embodiment of the refrigeration system described in the present invention, and its integration with external elements previously installed on site. The reference signs represent: 1.1 - first evaporation branch; 1.2 - second evaporation branch; 2 - expansion device; 3 - liquid separator; 4 - fluidic connection; 5 - valve means; 10 - external elements, such as evaporators and compressors. Figure 2 - representation of an embodiment of the refrigeration system described in the present invention. The reference signs represent: 1.1 - first evaporation branch; 1.2 - second evaporation branch; 2 - expansion device; 3 - liquid separator; 4 - fluidic connection; 5 - valve means; 6 - evaporator; 7.1 - first compressor branch; 7.2 - second compressor branch; 8 - compressor; 9 - high-pressure branch. DETAILED DESCRIPTION

[0022] The more general and advantageous configurations of the refrigeration system developed are described in the summary of the invention. Such configurations are detailed below in accordance with other advantageous and / or preferred embodiments of implementation of the system.

[0023] The present invention describes a refrigeration system, and incorporates an alternative to dry evaporators.

[0024] The system is comprised by at least two evaporation branches (1.1, 1.2), each of which configured to operate at a predefined evaporation level, an expansion device (2), such as an ejector, and a liquid separator (3). Further, to fluidically connect the referred system elements in an advantageous way, the system comprises a plurality of fluidic connections (4) and valve means (5).

[0025] A fluidic connection (4) may comprise standard or custom-made tubing device, that allows a fluid to flow within a closed conduit with a certain pressure. Valve means (5) is a flow control device that regulates and directs the flow of the fluid within a fluidic connection (4). According to the invention, the fluidic connections (4) and valve means (5) are arranged to fluidically connect: a first evaporation branch (1.1) to the expansion device (2), in such a way that the expansion device (2) is fed by the outlet of the first evaporation branch (1.1); the expansion device (2) to the liquid separator (3), in such a way that the liquid separator (3) is fed by the outlet of the expansion device (2); and the liquid separator (3) to at least a second evaporation branch (1.2), in such a way that said at least the second evaporation branch (1.2) is fed by a liquid obtained from the liquid separator (3).

[0026] Through this particular arrangement and combination between system elements (1.1, 1.2, 2, 3), fluidic connections (4) and valve means (5), it is possible to obtain an increase in heat transfer efficiency and a simplification in terms of system architecture, when compared to traditional refrigeration systems, resulting in a reduction in the overall space occupied by the system, making installation, maintenance and control tasks easier and less expensive.

[0027] In addition, as can be seen from figure 1, the use of this particular arrangement between system elements (1.1, 1.2, 2, 3) and respective fluid connections (4) and valve means (5) enables the integration of the refrigeration system with other external elements (10) that are previously installed on site, such as evaporators and / or compressors. More particularly, and as another consequence arising from the particular arrangement and combination between system elements (1.1, 1.2, 2, 3), fluidic connections (4) and valve means (5), the system may be integrated with semi-flooded evaporators without the need to have an additional tank working as a suction accumulator.

[0028] In one embodiment of the system, it may further comprise a plurality of evaporators (6). More particularly, each evaporation branch (1.1, 1.2) of the system is fluidically connected to at least one evaporator (6), being each evaporator (6) configured to operate at the respective branch's predefined evaporation level.

[0029] According to the invention, the system comprises at least two compressor branches (7.1, 7.2), each of which comprising at least one compressor (8). In this case, the plurality of fluidic connections (4) and valve means (5) are further arranged to fluidically connect: at least the second evaporation branch (1.2) to a first compressor branch (7.1), in such a way that the at least one compressor (8) of the first compressor branch (7.1) is fed by the outlet of at least the second evaporation branch (1.2); and the liquid separator (3), the first compressor branch (7.1) and a second compressor branch (7.2), in such a way that the at least one compressor (8) of the second compressor branch (7.2) is fed by gas obtained from the liquid separator (3) and by the outlet of the first compressor branch (7.1).

[0030] In this particular case, the system may further comprise at least one heat exchanger arranged in the fluidic connection (4) between at least the second evaporation branch (1.2) and the first compressor branch (7.1), in such a way that the first compressor branch (7.1) is fed by the outlet of the heat exchanger. Additionally, in another embodiment of the system, it may further comprise at least one heat exchanger arranged at the outlet of the first compressor branch (7.1), and the second compressor branch (7.2) being fed by a gas obtained from the liquid separator (3) and by the outlet of the heat exchanger.

[0031] As such, the system is equally designed to include all the necessary elements to carry out the refrigeration operation effectively, being able to operate as an independent refrigeration system, that is, including evaporators (6) and compressors (8), or as a refrigeration system comprising evaporation (1.1, 1.2) and compressor (7.1, 7.2) branches for connection to the respective elements (6, 8), which are already installed on site.

[0032] In another embodiment of the system, the plurality of fluidic connections (4) and valve means (5) are arranged to fluidically connect the liquid separator (3) to each of the at least two evaporation branches (1.1, 1.2), in such a way that each evaporation branch (1.1, 1.2) is fed by the liquid obtained from the liquid separator (3). In this particular configuration of the system, each evaporation branch (1.1, 1.2) may be configured to operate at a different evaporation level or at a same evaporation level.

[0033] In another embodiment, the system may also comprise a high-pressure branch (9), and the plurality of fluidic connections (4) and valve means (5) are further arranged to connect the high-pressure branch (9) to at least the expansion device (2), in such a way that the expansion device (2) is fed by the high-pressure branch (9). Additionally, the high-pressure branch (9) may comprise a set of fluidic connections (4) and valve means (5) arranged to connect the second compressor branch (7.2) to the expansion device (2), in such a way that the expansion device (2) is fed by the outlet of the at least one compressor (8) of the second compressor branch (7.2). In this context, the system may further comprise at least one oil separator and / or at least one heat exchanger, arranged in the fluidic connection (4) between the second compressor branch (7.2) and the expansion device (2).

[0034] According to the invention, each evaporation branch (1.1, 1.2) is configured to operate at a different evaporation level. In this embodiment, the first evaporation branch (1.1) is configured to operate at a medium evaporation level (MT), and at least the second evaporation branch is configured to operate at a low evaporation level (LT). Additionally, the plurality of fluidic connections (4) and valve means (5) are arranged to fluidically connect: (i.) the first evaporation branch (1.1) to the expansion device (2), in such a way that the expansion device (2) is fed by the outlet of the first evaporation branch (1.1); and (ii.) the liquid separator (3) to at least the second evaporation branch (1.2), in such a way that at least the second evaporation branch (1.2) is fed by the liquid obtained from the liquid separator (3). More particularly, a medium evaporation level may correspond to an evaporation temperature between -20º C to 0ºC and a low evaporation level may correspond to an evaporation temperature between -40ºC to - 20ºC. Additionally, the system may further comprise a high-pressure branch (9), and the plurality of fluidic connections (4) and valve means (5) are further arranged to connect said high-pressure branch (9) to the first evaporation branch (1.1), in such a way that the first evaporator branch (1.1) is fed by the high-pressure branch (9).

[0035] According to the invention, the plurality of fluidic connections (4) and valve means (5) are further arranged to fluidically connect at least the second evaporator branch (1.2) to the first compressor branch (7.1), in such a way that the at least one compressor (8) of the first compressor branch (7.1) is fed by the outlet of at least the second evaporator branch (1.2). Additionally, the high-pressure branch (9) comprises a set of fluidic connections (4) and valve means (5) arranged to connect the second compressor branch (7.2) to the first evaporator branch (1.1), in such a way that the first evaporator branch (1.1) is fed by the outlet of the at least one compressor (8) of the second compressor branch (7.2). The system may further comprise at least one oil separator and / or at least one heat exchanger, arranged in the fluidic connection (4) between the second compressor branch (7.2) and the first evaporator branch (1.1).

[0036] In another embodiment, the system may further comprise at least one heat exchanger. Said heat exchanger is arranged in the fluidic connection (4) between the high-pressure branch (9) and the first evaporator branch (1.1), in such a way that the heat exchanger is fed by the high-pressure branch (9) and the first evaporator branch (1.1) is fed by the outlet of the heat exchanger.

[0037] As will be clear to one skilled in the art, the present invention should not be limited to the embodiments described. The scope of the present invention is solely defined by the appended claims.

Claims

1. Refrigeration system comprising: At least two evaporation branches (1.1, 1.2), each of which configured to operate at a predefined evaporation level; An expansion device (2), such as an ejector; A liquid separator (3); At least two compressor branches (7.1, 7.2), each of which comprising at least one compressor (8); A high-pressure branch (9); A plurality of fluidic connections (4) and valve means (5) arranged to fluidically connect: a first evaporation branch (1.1) to the expansion device (2), in such a way that the expansion device (2) is fed by the outlet of the first evaporation branch (1.1); the expansion device (2) to the liquid separator (3), in such a way that the liquid separator (3) is fed by the outlet of the expansion device (2); the liquid separator (3) to at least a second evaporation branch (1.2), in such a way that said at least the second evaporation branch (1.2) is fed by a liquid obtained from the liquid separator (3); at least the second evaporation branch (1.2) to a first compressor branch (7.1), in such a way that the at least one compressor (8) of the first compressor branch (7.1) is fed by the outlet of at least the second evaporation branch (1.2); the liquid separator (3), the first compressor branch (7.1) and a second compressor branch (7.2), in such a way that the at least one compressor (8) of the second compressor branch (7.2) is fed by gas obtained from the liquid separator (3) and by the outlet of the first compressor branch (7.1); and the high-pressure branch (9) to the first evaporation branch (1.1), in such a way that the first evaporator branch (1.1) is fed by the high-pressure branch (9); and wherein, each evaporation branch (1.1, 1.2) is configured to operate at a different evaporation level; the first evaporation branch (1.1) is configured to operate at a medium evaporation level (MT), and at least the second evaporation branch (7.2) is configured to operate at a low evaporation level (LT); the high-pressure branch (9) comprises a set of fluidic connections (4) and valve means (5) arranged to: connect the second compressor branch (7.2) to the first evaporator branch (1.1), in such a way that the first evaporator branch (1.1) is fed by the outlet of the at least one compressor (8) of the second compressor branch (7.2).

2. System according to claim 1, further comprising a plurality of evaporators (6), wherein each evaporation branch (1.1, 1.2) being fluidically connected to at least one evaporator (6); each evaporator (6) being configured to operate at the respective branch's predefined evaporation level.

3. System according to claim 1, further comprising at least one heat exchanger arranged in the fluidic connection (4) between at least the second evaporation branch (1.2) and the first compressor branch (7.1), in such a way that the first compressor branch (7.1) is fed by the outlet of the heat exchanger.

4. System according to claims 1 or 3, further comprising at least one heat exchanger arranged at the outlet of the first compressor branch (7.1); the second compressor branch (7.2) being fed by a gas obtained from the liquid separator (3) and by the outlet of the heat exchanger.

5. System according to any of the previous claims, wherein the plurality of fluidic connections (4) and valve means (5) are arranged to fluidically connect the liquid separator (3) to each of the at least two evaporation branches (1.1, 1.2), in such a way that each evaporation branch (1.1, 1.2) is fed by the liquid obtained from the liquid separator (3); and wherein, each evaporation branch (1.1, 1.2) is configured to operate at a different evaporation level or at a same evaporation level.

6. System according to claim 5, wherein, the plurality of fluidic connections (4) and valve means (5) are further arranged to connect the high-pressure branch (9) to the expansion device (2), in such a way that the expansion device (2) is fed by the high-pressure branch (9).

7. System according to claims 1 and 6, wherein the high-pressure branch (9) comprises a set of fluidic connections (4) and valve means (5) arranged to: connect the second compressor branch (7.2) to the expansion device (2), in such a way that the expansion device (2) is fed by the outlet of the at least one compressor (8) of the second compressor branch (7.2).

8. System according to claim 7, further comprising at least one oil separator and / or at least one heat exchanger, arranged in the fluidic connection (4) between the second compressor branch (7.2) and the expansion device (2).

9. System according to claim 1 wherein a medium evaporation level corresponds to an evaporation temperature between -20º C to 0ºC; and a low evaporation level corresponds to an evaporation temperature between -40ºC to -20ºC.

10. System according to claim 1, further comprising at least one oil separator and / or at least one heat exchanger, arranged in the fluidic connection (4) between the second compressor branch (7.2) and the first evaporator branch (1.1).

11. System according to claims 1 or 10, further comprising at least one heat exchanger; said heat exchanger being arranged in the fluidic connection (4) between the high-pressure branch (9) and the first evaporator branch (1.1), in such a way that: - the heat exchanger is fed by the high-pressure branch (9); and - the first evaporator branch (1.1) is fed by the outlet of the heat exchanger.