WO2019043595A1

WO2019043595A1 - Refrigeration device

Info

Publication number: WO2019043595A1
Application number: PCT/IB2018/056588
Authority: WO
Inventors: Maurizio Ascani
Original assignee: Angelantoni Test Technologies S.R.L. - In Breve Att S.R.L.
Priority date: 2017-09-01
Filing date: 2018-08-29
Publication date: 2019-03-07
Also published as: IT201700098472A1

Abstract

Refrigeration device (100) having a closed circuit (C) comprising one main line (M) along which one main compressor (101), one condenser (102), one expansion valve (103) and one evaporator (104) are arranged, one turbocompressor (105) having one turbine (106) and one centrifugal compressor (107), wherein said centrifugal compressor (107) is arranged along said main line (M) between said at least one evaporator (104) and said at least one main compressor (101), said closed circuit (C) comprises one secondary branch (B) to fluidically connect the outlet (O) of said main compressor (101) to the inlet (I) of said main compressor (101), wherein the inlet (IN) of the secondary branch (B) is arranged between said main compressor (101) and said condenser (102) and the outlet (OUT) of the secondary branch (B) is arranged between said centrifugal compressor (107) and said at least one main compressor (101).

Description

"Refrigeration device"

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FIELD OF THE INVENTION

The present invention concerns a refrigeration device. In particular, this invention refers to a refrigeration device particularly adapted for very low temperature systems. KNOWN PRIOR ART

According to the known art, a refrigeration device for a climatic chamber comprises a closed circuit in which a coolant is circulating. This closed circuit comprises, in its essential layout, a main compressor for the circulation of the fluid inside the closed circuit, a condenser, an expansion thermostatic valve and an evaporator.

In this refrigeration device of known art, technical limitations make it impossible to lower the pressure under a certain value, and therefore the temperature of the coolant at the outlet of the evaporator, without being forced to excessively increase the complexity of the refrigeration device itself. In fact, under 0.8 bars, the main compressor is no longer able to raise the pressure back to the desired value to make the fluid circulate along the entire closed circuit and to, therefore, allow the normal operations of the system. As a result of this limitation, the pressure at the outlet of the evaporator is at the maximum close to the atmospheric pressure and, therefore, the minimum temperature achievable by this refrigeration device, in its most simple layout, i.e. comprising its essential elements and normal coolants, is of about -40°C. However, in some applications, it is useful to obtain a greater refrigeration level and, therefore to ultimately have the coolant at the outlet of the evaporator also reach temperatures closer to -80°C which, with normal coolants, would correspond to pressures close to 0.2 - 0.3 bars. This is only obtainable by considerably increasing the complexity of the system, such as by using more coolants for example, and therefore by providing another cooling circuit, which would consequently make it extremely difficult and considerably expensive to achieve the refrigeration device.

Therefore, an object of the present invention is to implement a refrigeration device allowing a very high refrigeration level to be achieved by using, however, a closed refrigeration circuit in its essential layout, i.e. provided with a single coolant circulating inside the system. Finally, object of the present invention is to implement a refrigeration device able to perform the aforesaid objects by means of a simple and easy to assemble structure. Finally, an object of the present invention is to implement a refrigeration device achieved by using existing devices on which to carry out few and simple system modifications.

SUMMARY OF THE INVENTION

These and other objects are achieved by means of a refrigeration device having a closed circuit in which a given flow rate of coolant is circulating, said closed circuit comprising at least one main line along which at least one main compressor, at least one condenser, at least one expansion valve and at least one evaporator are arranged, said refrigeration device further comprising at least one turbocompressor having at least one turbine and at least one centrifugal compressor, wherein said centrifugal compressor is arranged along said main line between said at least one evaporator and said at least one main compressor, characterized in that said closed circuit comprises at least one secondary branch to fluidically connect the outlet of said main compressor to the inlet of said main compressor, wherein the inlet of said at least one secondary branch is arranged along said main line, between said main compressor and said condenser, and the outlet of said at least one secondary branch is arranged between said centrifugal compressor and said at least one main compressor, said at least one turbine of said turbocompressor being arranged along said at least one secondary branch to be fed by the bleed flow rate of the coolant circulating along said at least one secondary branch.

In practice, this solution makes it possible to use the bleed flow rate of the coolant having an extremely high pressure, to feed the turbine of the turbocompressor and to therefore provide the power needed to the centrifugal compressor in order to compress the fluid that, at the outlet of the evaporator, is under the atmospheric pressure. This solution further makes it possible to work with a fluid at the outlet of the evaporator at a pressure of 0.2 bars and to bring it to a pressure that is compatible with the operations of the normal compressors used in the refrigeration devices of known art.

Furthermore, the refrigeration device comprises at least one heat exchanger arranged along said at least one secondary branch, upstream of said at least one turbine of said turbocompressor, to cool said bleed fluid flow rate. In fact, the fluid at the outlet of the main compressor is at an excessively high temperature compared to the optimal one for the refrigeration cycle.

Advantageously, said at least one heat exchanger is of air or water type. Moreover, the hydraulic circuit of said at least one heat exchanger is outside of said closed circuit. According to the invention, the refrigeration device comprises at least one on-off valve arranged along said at least one secondary branch to vary the bleed fluid flow rate circulating along said at least one secondary branch.

Also, said refrigeration device comprises at least one control unit controlling, depending on the pressure and/or temperature measured at the outlet of said at least one evaporator, the opening/closing of said at least one on-off valve to allow/prevent the passing of the bleed fluid flow rate along said secondary branch. This makes it possible to vary the power available at the centrifugal compressor of the turbocompressor according to the need. Under operational conditions at the pressures of the coolant at the outlet of the standard evaporator, or close to the atmospheric pressures, the bleed fluid flow rate will be null, therefore the on-off valve will be closed, while under threshold conditions in which the pressure of the coolant at the outlet of the evaporator is lower than the threshold pressure established at less than 0.8 bars for example, then the valve will allow the flow rate to completely pass along said at least one secondary branch.

Moreover, the refrigeration device comprises at least one pressure and/or temperature sensor arranged downstream of said at least one evaporator, to measure the temperature and/or pressure of the coolant circulating at the outlet of at least said one evaporator.

According to another embodiment of the invention, the refrigeration device comprises a second main compressor arranged along said main line, between said first main compressor and said centrifugal compressor of said turbocompressor, wherein said at least one secondary branch fluidically connects the outlet of said first main compressor to the outlet of said second main compressor.

According to the invention, a method is provided for the operations of a refrigeration device according to one or more of claims 1 to 8, characterized by comprising the step a) of feeding said turbine of said turbocompressor by means of a bleed flow rate of said flow rate of coolant circulating in said closed circuit and passing along said at least one secondary branch to fluidically connect the outlet of said main compressor to the inlet of said main compressor, wherein the inlet of said at least one secondary branch is arranged along said main line between said main compressor and said condenser and the outlet of said at least one secondary branch is arranged between said centrifugal compressor and said at least one main compressor.

Moreover, said step a) comprises the step al) of measuring the pressure and/or temperature of the coolant at the outlet of said at least one evaporator and the step a2) of controlling the opening/closing of said at least one on-off valve to allow/prevent the passing of the bleed fluid flow rate along said secondary branch depending on the results obtained in said step al).

BREIF DESCRIPTION OF THE FIGURES

These and other aspects of the present invention will become clearer by the following detailed description of a preferred embodiment provided herein by way of example only and without limitations, with reference to the accompanying figures, in which: figure 1 shows a view of the operational layout of a refrigeration device according to a first embodiment of the invention;

figure 2 shows a view of the operational layout of a refrigeration device according to a second embodiment of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE PRESENT INVENTION

With reference to the figures above, a refrigeration device 100 according to the invention is shown.

Figure 1 shows a refrigeration device 100 according to a first embodiment of the invention. This refrigeration device 100 has a closed circuit C in which a given flow rate P of coolant is circulating. This closed circuit C comprises a main line M along which a main compressor 101 , a condenser 102, an expansion valve 103 and an evaporator 104 are arranged in a known way. Advantageously, according to the invention, the device 100 comprises a turbocompressor 105 having a turbine 106 and a centrifugal compressor 107 spliced on the same axis. The centrifugal compressor 107 is arranged along the main line M between the evaporator 104 and the main compressor 101.

According to the invention, the closed circuit C further comprises a secondary branch B to fluidically connect the outlet O of the main compressor 101 to the inlet I of the main compressor 101 itself, in a position along the main line M comprised between the main compressor 101 itself and the centrifugal compressor 107 of the turbocompressor 105. In practice, the inlet IN of the secondary branch B is arranged along the main line M between the main compressor 101 and the condenser 102, while the outlet OUT of the secondary branch B is arranged along said main line M, downstream of the evaporator 104, between the main compressor 101 and the centrifugal compressor 107 of the turbocompressor 105.

In particular, the turbine 106 of the turbocompressor 105 is arranged along this secondary branch B along which the bleed flow rate PI is circulating. Therefore, in practice, a portion of the circulating flow rate PI is used inside the closed circuit C to feed the turbine 106 and to therefore allow the operations of the centrifugal compressor 107 that allows to raise the pressure and temperature of the fluid at the outlet of the evaporator. This solution is extremely advantageous since the bleed flow rate PI , upstream of the compressor 101 , is provided with a pressure capable of feeding the turbine 106 so as to provide it with the adequate power needed to allow the correct operations of the compressor 107 and, therefore, to also be able to work with the very low pressures downstream of the evaporator 104, even lower than 0.8 bars.

Moreover, the refrigeration device 100 comprises a heat exchanger 108 arranged along the secondary branch B, upstream U of the turbine 106 of the turbocompressor 105, to cool the bleed flow rate PI and to therefore avoid having to reintroduce an excessively hot coolant inside the main compressor 101. Specifically, the heat exchanger 108 is outside of the closed circuit C. Preferably, the hydraulic circuit of the heat exchanger 108, which in case of the embodiment shown works with water, is outside of the closed circuit C. In other embodiments, the heat exchanger 108 can work with air without thereby departing from the scope of protection of the present invention.

Always according to the embodiment herein described, the refrigeration device 100 comprises an on-off valve 109 arranged along the secondary branch B to vary the bleed fluid flow rate PI circulating along the secondary branch B according to the need. In particular, the refrigeration device 100 comprises a control unit CU controlling, depending on the pressure measured at the outlet of the evaporator 104, the opening/closing of the on-off valve 109 to allow/prevent the passing of the bleed fluid flow rate P 1 along the secondary branch B.

In this embodiment, the refrigeration device 100 further comprises a pressure sensor 1 10 arranged downstream of the evaporator 104 to measure the pressure of the coolant at the outlet of the evaporator 104 and to communicate this measure to the control unit CU so that it can appropriately control the opening/closing of the on-off valve 109. In an alternative embodiment, the refrigeration device 100 comprises a temperature sensor 1 10 instead of a pressure sensor, to measure the temperature of the coolant at the outlet of the evaporator 104 and to communicate this measure to the control unit CU, so that it can appropriately control the opening/closing of the on-off valve 109. Therefore, if the coolant level requested by the user is not high, then the pressure at the outlet of the evaporator is always greater than 0.8 bars and, therefore, the valve 109 prevents the bleed flow rate PI from passing along the secondary branch B and the refrigeration device 100 works in a traditional way. If the device 100 is required to provide a high level of refrigeration, thus reaching extremely low temperatures even below -60°C, then the pressure of the coolant at the outlet of the evaporator 104 is lower than 0.8 bars and, therefore, the valve 109 allows the bleed flow rate PI to pass along the secondary branch B for the feeding of the turbine 106 and, therefore, of the centrifugal compressor 107. This way, a coolant is available for the main compressor 101 , at a pressure allowing it to work within its nominal flow.

Figure 2 shows a second embodiment that differs from the first since the refrigeration device 100 further comprises a second main compressor 1 1 1 , i.e. a first stage of compression, arranged along the main line M, between the first main compressor 101 and the centrifugal compressor 107 of the turbocompressor 105. The secondary branch B fluidically connects the outlet O of the first main compressor 101 to the outlet O' of the second main compressor 1 1 1.

Still according to the invention, the method for the operations of the refrigeration device 100 comprises, both in the first and second embodiment of the invention, in addition to the preliminary step of activating the refrigeration device 100 according to the known art, i.e. of making the flow rate of coolant circulating through the main line M, making it therefore pass from the main compressor 101 , to the condenser 102, to the expansion valve 103 and up to the evaporator 104, before restarting the cycle again, the step a) of feeding the turbine 106 of the turbocompressor 105 by means of a bleed flow rate PI of the flow rate of coolant P circulating inside the closed circuit C and passing through a secondary branch B to fluidically connect the outlet O of the main compressor 101 to the inlet I of the main compressor 101 itself, wherein the inlet IN of the secondary branch B is arranged along the main line M between the main compressor 101 and the condenser 102, while the outlet OUT of the secondary branch B is arranged between the centrifugal compressor 107 of the turbocompressor 105 and the main compressor 101.

The aforesaid bleed flow rate PI is at a pressure so as to ensure the power needed for the centrifugal compressor 107 of the turbocompressor 105 to work, also with fluids at very low pressures, i.e. even lower than the atmospheric pressure and up to 0.2 bars. Still according to the method, the step a) further comprises the step al) of measuring the pressure of the coolant at the outlet of the evaporator 104 and the step a2) of controlling the opening/closing of the on-off valve 109 to allow/prevent the passing of the bleed fluid flow rate PI along the secondary branch B depending on the results obtained in step al).

Therefore, in practice, if the pressure at the outlet of the evaporator is greater than 0.8 bars, then the valve 109 prevents the bleed flow rate from passing along the secondary branch B, whereas if the pressure of the coolant at the outlet of the evaporator 104 is lower than 0.8 bars, for example when a greater refrigeration level is required, then the valve 109 allows the bleed flow rate PI to pass along the secondary branch B. It should be noted that the 0.8 bar threshold indicated herein could vary depending on the type of main compressor 101 selected, or on the type of centrifugal compressor 107 selected, or on the refrigeration needs provided for that particular refrigeration device 100.

In an alternative embodiment, during step al) the temperature of the coolant at the outlet of the evaporator 104 is measured to allow/prevent, during step a2), the passage of the bleed fluid flow rate PI along the secondary branch B depending on the results obtained.

During step al ) the temperature can be measured alternatively to or in combination with the measurement of the pressure of the coolant.

Claims

1. Refrigeration device (100) having a closed circuit (C) in which a given flow rate (P) of coolant circulates, said closed circuit comprising at least one main line (M) along which at least one main compressor (101), at least one condenser (102) at least one expansion valve (103) and at least one evaporator ( 104) are arranged, said refrigeration device further comprising at least one turbocompressor (105) having at least one turbine (106) and at least one centrifugal compressor (107), wherein said centrifugal compressor (107) is arranged along said main line (M) between said at least one evaporator (104) and said at least one main compressor (101), characterized in that said closed circuit (C) comprises at least one secondary branch (B) to fluidically connect the outlet (O) of said main compressor (101) to the inlet (I) of said main compressor (101), wherein the inlet (IN) of said at least one secondary branch (B) is arranged along said main line (M) between said main compressor (101) and said condenser (102) and the outlet (OUT) of said at least one secondary branch (B) is arranged between said centrifugal compressor (107) and said at least one main compressor (101), said at least one turbine (106) of said turbocompressor (105) being arranged along said at least one secondary branch (B) to be fed by the bleed flow rate (PI) circulating along said at least one secondary branch (B).

2. Refrigeration device according to claim 1 , characterized by comprising at least one heat exchanger (108) arranged along said at least one secondary branch (B), upstream

(U) of said at least one turbine (106) of said turbocompressor (105) to cool said bleed flow rate (PI).

3. Refrigeration device according to claim 2, characterized in that said at least one heat exchanger is of air or water type.

4. Refrigeration device according to claim 2 or 3, characterized in that the air or water circuit of said at least one heat exchanger (108) is outside of said closed circuit (C).

5. Refrigeration device according to one or more of claims 1 to 4, characterized by comprising at least one on-off valve (109) arranged along said at least one secondary branch (B) to vary the bleed fluid flow rate (PI) circulating^" along said at least one secondary branch (B).

6. Refrigeration device according to claim 5, characterized by comprising at least one control unit (CU) controlling, depending on the pressure and/or temperature measured at the outlet of said at least one evaporator (104), the opening/closing of said at least one on-off valve (109) to allow/prevent the passing of the bleed fluid flow rate (PI) along said secondary branch (B).

7. Refrigeration device according to claim 6, characterized by comprising at least one pressure and/or temperature sensor (110) arranged downstream of said at least one evaporator (104) to measure the temperature and/or pressure of the circulating coolant at the outlet of said at least one evaporator.

8. Refrigeration device according to one or more of claims 1 to 7, characterized by comprising a second main compressor (1 1 1) arranged along said main line (M), between said first main compressor (101) and said centrifugal compressor (107) of said turbocompressor (105).

9. Method for operating a refrigeration device (100) according to one or more of claims 1 to 8, characterized by comprising the step a) of feeding said turbine (106) of said turbocompressor (107) by a bleed flow rate (PI) of said flow rate (P) of coolant circulating in said closed circuit (C) and passing through said at least one secondary branch (B) to fluidically connect the outlet (O) of said main compressor (101) to the inlet (I) of said main compressor (101), wherein the inlet (IN) of said at least one secondary branch (B) is arranged along said main line (M) between said main compressor (101) and said condenser (102) and the outlet (OUT) of said at least one secondary branch (B) is arranged between said centrifugal compressor (107) and said at least one main compressor.

10. Method according to claim 9, characterized in that said step a) comprises the step al) of measuring the pressure and/or temperature of the coolant at the outlet of said at least one evaporator (104) and the step a2) of controlling the opening/closing of said at least one on-off valve (109) to allow/prevent the passing of the bleed fluid flow rate (PI) along said secondary branch (B) depending on the results obtained in said step al).