PL246608B1 - Cooling system and refrigeration device, especially on a marine unit - Google Patents

Abstract

The cooling system, especially on a marine unit, comprises a tank (1) for a refrigerant in the form of carbon dioxide CO2, connected via an expansion valve (5.1) to an evaporator (5.2) in the freezing chamber (5) and via an expansion valve (6.1) to an evaporator (6.2) in the cooling chamber (6). The outlet of the evaporator (5.2) in the freezing chamber (5) and the outlet of the evaporator (6.2) in the cooling chamber (6) are connected to the first and second stage compressors (7, 8) and to the refrigerant tank (1). The outlet of the refrigerant in the form of carbon dioxide CO2 from the second stage compressor (8) is connected via an oil separator (11) to the inlet of this refrigerant to the cooler (13). The outlet of the refrigerant from the cooler (13) is connected via a high pressure expansion valve (4.4) to the inlet of this refrigerant to the refrigerant tank (1). The refrigerant outlet from the compressor (7) of the first stage and the refrigerant inlet to the compressor (8) of the second stage are connected, via a bypass expansion valve (10), to the refrigerant tank (1). The refrigerant outlet from the oil separator (11) to the cooler (13) is connected to the refrigerant tank (1) via a bypass solenoid valve (14.1). The gaseous medium outlet from the cooler (13) to the refrigerant tank (1) is equipped with a non-return valve. The cooler (13) is supplied with refrigerant in the form of sea water.

Description

Description of the invention

The subject of the invention is a cooling system intended especially for use on a marine unit; floating as well as anchored at sea. The subject of the invention is also a cooling device, especially on a marine unit. The solution concerns a cooling system and a cooling device where the cooling agent is carbon dioxide. The subject of the invention is primarily a provisions cooler on a marine unit.

There are a number of known solutions for refrigeration devices and systems intended for use at sea. A number of these solutions operate using a refrigerant in the form of carbon dioxide CO2, both on land and in marine conditions on floating units and on anchored units.

In the solution known from the publication of the international application on WO 2021/151392, a cyclic refrigeration system with phase change of carbon dioxide is disclosed. The refrigeration system includes: a tank for liquid carbon dioxide used to store liquid CO2; an evaporation section connected to the liquid carbon dioxide storage tank and used to perform pressure reduction and evaporation of liquid CO2 to obtain gaseous CO2. The pressure increasing section is connected to the evaporation chamber and used to increase the pressure and cool the high temperature gaseous CO2. The system further comprises a condensation section connected independently to the pressure increase section and the tank for storing liquid carbon dioxide. The condensation section is used to convert high temperature and high pressure gaseous CO2 to liquid CO2. The system according to the invention comprises a liquid/air heat exchanger connected to the liquid of the evaporation section for receiving a low temperature aqueous solution of ethylene glycol and exchanging heat with the circulating air. The cyclic carbon dioxide phase change refrigeration system of the present invention realizes cooling by using the liquid-gas and gas-liquid phase change of CO2. In this solution, an aqueous solution of ethylene glycol is used as the heat exchange medium between carbon dioxide and air.

In another solution, disclosed in the publication of the international application no. WO 2021/089000, a system for compressing a refrigerant vapor with carbon dioxide and a method of operating said system are presented. The refrigerant vapor compression system includes a compression device, an expansion tank placed in the refrigerant circuit, an intermediate heat exchanger removing the heat of the refrigerant and a heat exchanger absorbing the heat of the refrigerant. The system also includes a compressor discharge circuit including a refrigerant line establishing a refrigerant flow communication between the intermediate unit of the pressure stage of the compression device and the refrigeration circuit at a location beyond the heat absorbing refrigerant heat exchanger and upstream of the suction inlet to the compression device. The system also includes a flow control device in the relief circuit placed in said refrigerant line. In response to at least one system operating parameter detected by at least one sensor, the controller selectively sets the unload flow control device to maintain operation of the refrigerant vapor compression system below a preselected upper pressure limit.

In another solution according to WO 2006/022829, a refrigeration circuit for circulating a refrigerant in a specific flow direction comprises, in order in accordance with the flow direction of the refrigerant, a heat exchanger, a tank with a liquid phase of the refrigerant and an expansion gas line. A medium temperature section and a low temperature section are located downstream of the tank. The medium and low temperature sections contain in the flow direction an expansion device, an evaporator and a compressor. The refrigeration circuit further comprises a liquid line connecting the liquid line from the tank to at least one of the medium and low temperature sections. The circuit has an internal heat exchanger and an expansion gas line connecting the expansion gas line of the tank via an internal heat exchanger to the inlet of the low temperature compressor. The internal heat exchanger transfers useful heat from the liquid flowing through the liquid line to the expansion gas flowing through the expansion gas line.

Another solution, known from the document WO 2022/053503, relates to a refrigeration system comprising at least one compressor for a first stage of compression of a refrigerant in the form of carbon dioxide, a main heat removal system for cooling the refrigerant, one or more high-pressure expansion devices for reducing the pressure of the CO2 refrigerant, a tank for storing the CO2 refrigerant, one or more high-pressure expansion devices, an evaporator and a device for regulating the pressure in the tank. The refrigeration system according to this known solution further comprises an auxiliary refrigeration unit comprising an additional compressor adapted to compress at least part of the refrigerant and then to direct the compressed refrigerant to the heat removal system.

In a further solution, known from international application no. WO 2021/012725, a system with a refrigerant in the form of carbon dioxide and a method of its operation are presented. The refrigeration system comprises a compressor, a condenser, a liquid storage device and an evaporator. A suction unit is placed between the compressor and the condenser, and a second suction unit is connected to the liquid storage device and to the gas-liquid separator. The gas-liquid separator is placed between the condenser and the liquid storage device. Gaseous carbon dioxide in the liquid storage device or the gas-liquid separator can be sucked back into the pipeline between the compressor and the condenser by means of the suction unit.

In most known solutions of cooling systems and cooling devices, a cooling system is provided containing a refrigerant tank, where the refrigerant is transferred under pressure to the evaporator unit, where the temperature of this agent is reduced as a result of evaporation. The problem to be solved is the additional reduction of the temperature of the refrigerant at the inlet to the high-pressure expansion valve 4.4, before the pipeline supplying this working agent to the tank. The invention also solves the problem of uncontrolled switching on and off of compressors due to pressure fluctuations of the refrigerant in the circuit.

According to the invention, the cooling system, especially on a marine unit, comprises a tank of refrigerant in the form of carbon dioxide CO2, connected via an expansion valve to the evaporator in the freezing chamber and via an expansion valve to the evaporator in the cooling chamber, where the outlet of the evaporator in the freezing chamber and the outlet of the evaporator in the cooling chamber are connected to the first and second stage compressors and to the refrigerant tank. The outlet of the refrigerant in the form of carbon dioxide CO2 from the second stage compressor is connected via an oil separator to the inlet of this refrigerant to the gas cooler, while the outlet of the refrigerant from the gas cooler is connected via a high-pressure expansion valve to the inlet of this refrigerant to the refrigerant tank. The outlet of the refrigerant from the first stage compressor and the inlet of the refrigerant to the second stage compressor are connected via a bypass expansion valve to the refrigerant tank.

According to the invention, the cooling system is characterized in that the refrigerant outlet from the oil separator to the cooler is connected to the refrigerant tank via a bypass solenoid valve, and the gas medium outlet from the gas cooler to the refrigerant tank is equipped with a non-return valve, the gas cooler being supplied with a refrigerant in the form of sea water.

In a cooling system, in a preferred version of the solution according to the invention, the bypass solenoid valve is controlled by the suction pressure difference between the first-stage compressor and the second-stage compressor.

The liquid refrigerant outlet from the refrigerant tank is connected to the expansion valves of the freezing chamber and the cooling chamber, preferably via a dehydration filter.

The refrigerant outlet from the freezing chamber evaporator is advantageously connected to the suction inlet of the first-stage compressor, the pressure outlet of which is connected to the refrigerant outlet from the freezing chamber evaporator and to the inlet to the second-stage compressor, and via an oil separator and a cooler to the inlet to the refrigerant tank.

According to the invention, a refrigeration device, especially on a marine unit, comprises a refrigerant tank in the form of carbon dioxide CO2 mounted in a frame, connected by a pipeline through an expansion valve to the evaporator in the freezing chamber, and by an expansion valve to the evaporator in the cooling chamber. The outlet pipeline from the evaporator in the freezing chamber, and the outlet pipeline from the evaporator in the cooling chamber are connected to the first and second stage compressors, and are connected by a pressure-suction pipeline to the refrigerant tank. The refrigerant outlet from the second stage compressor is connected by a branch pipeline to the refrigerant inlet nozzle to the gas cooler, and the refrigerant outlet from the gas cooler is connected by a refrigerant pipeline, through a high-pressure expansion valve, to the inlet nozzle of this working medium to the tank. The outlet of the refrigerant discharge-suction pipeline from the first-stage compressor and the refrigerant inlet to the second-stage compressor are connected by a bypass line via a bypass expansion valve to the refrigerant tank.

According to the invention, the refrigeration device according to the invention is characterized in that the refrigerant pipeline from the oil separator to the gas cooler is connected by a bypass pipeline to the tank, wherein the bypass pipeline is equipped with an electromagnetic valve, and the refrigerant return pipeline from the gas cooler to the refrigerant tank is equipped with a non-return valve, wherein the gas cooler is supplied with a refrigerant in the form of sea water.

In a preferred version of the solution according to the invention, the solenoid valve is controlled by the suction pressure difference between the first-stage compressor and the second-stage compressor.

The seawater tube assembly and the gas cooler tube sheets are preferably made of titanium.

The refrigerant outlet pipeline from the refrigerant tank is advantageously connected to the expansion valves of the freezing chamber and the cooling chamber via a drainage filter.

In the solution according to the invention, the refrigeration system was equipped with an additional bypass pipeline connecting the compressor discharge pipeline with the refrigerant return pipeline to the tank via an additional solenoid valve. The pipeline from the gas cooler to the tank was equipped with a non-return valve. These changes protect against pressure drops in the system, which was the cause of compressors switching off and periodically leading to intermittent operation, which occurred both at start-up and during system operation. In this solution, the operation of the bypass pipeline together with the solenoid valve is dependent on the operation of the freezing chamber and the cooling chamber, the setting of the refrigerant pressures, which are different for each of the chambers. A pressure drop below the set values causes the valve and the bypass pipeline to open, reaching the set values causes the bypass valve to close. On the other hand, the proposed non-return valve guarantees the flow of the refrigerant to the tank, and thus protects the system against the return flow of the refrigerant through the gas cooler.

The subject of the invention is shown in an embodiment in the attached drawings, in which the subsequent figures of the drawings illustrate:

Fig. 1 - block diagram of the cooling system.

Fig. 2 - refrigeration device.

Fig. 3 - refrigerant tank in half-section view

Fig. 4 - the tank according to Fig. 3 in a cross-section through a plane consistent with the longitudinal axis of symmetry.

Fig. 5 - gas refrigerant cooler.

Fig. 6 - the cooler according to Fig. 5 in a cross-section consistent with the longitudinal axis of symmetry.

Fig. 7 - the cooler according to Fig. 5 in a cross-section perpendicular to the longitudinal axis of symmetry, in the area of the sea water inlet cover.

Fig. 8 - the radiator in cross-section according to Fig. 7 within the coolant flow pipes.

Fig. 9 - interior of the radiator according to Fig. 5.

Fig. 10 - tube configurations inside the cooler according to Fig. 5.

Figure 1 shows an example of a block diagram of a cooling system according to the invention. In the cooling system, the refrigerant is carbon dioxide CO2, also referred to in refrigeration by the symbol R744. The refrigeration system comprises a tank 1 of a refrigerant in the form of a two-phase gas-liquid mixture of carbon dioxide CO2. The internal pressure in the tank 1 during operation is designed to be from about 40 bar to a maximum of 80 bar. In this example of an embodiment, the operating pressure in the tank 1 is 40 bar.

Tank 1, as shown in drawings fig. 2, fig. 3 and fig. 4, has the form of a vertical drum with an upper bottom 2 and a lower bottom 3. In tank 1, in its lower part during the operation of the system, there is a refrigerant in the form of a liquid, while in the upper part there is the same refrigerant but in gaseous form. From the zone of the lower bottom 3 of tank 1, a refrigerant in the form of a liquid is collected at a pressure of 40 bar, while to the zone of the upper bottom 2 of tank 1, through the line 4.2 with the expansion valve 4.4, the refrigerant in the form of a gas also at a pressure of 40 bar is returned. The lower bottom 3 is connected by the line 4.1 of the liquid refrigerant, through the dehydration filter 4.3 with the freezing chamber 5 and with the cooling chamber 6 of the cooling system. In this embodiment, the temperature in the freezing chamber is maintained at -20°C. Inside the evaporator the temperature is -28°C, pressure 15 bar. In the cooling chamber 6 respectively, in this embodiment the parameters are: +4°C, in the evaporator 6.2 the temperature is -4°C and the pressure is 30 bar.

In the freezing chamber 5, the line 4.1 is supplied through the expansion valve 5.1 to the evaporator 5.2, from where the refrigerant in the form of carbon dioxide CO2, after evaporation, is supplied through the suction pipeline 5.3 to the compressor 7, also marked in Fig. 1 with the symbol LT. The outlet of the evaporator 5.2 from the freezing chamber 5 is connected to the inlet to the compressor 7, where the suction pressure of the compressor 5 in this embodiment is 15 bar.

In the cooling chamber 6, the line 4.1 is fed through the expansion valve 6.1 to the evaporator 6.2, from where the refrigerant, after evaporation, is fed through the pipeline 6.3 connecting with the discharge pipeline 7.1 from the compressor 7 to the second-stage compressor 8, also marked with the symbol MT in Fig. 1.

A refrigerant pipeline 6.3 from the evaporator 6.2 of the cooling chamber 6 is also connected to the line 7.1 connecting the outlet of the first-stage compressor 7 with the inlet to the second-stage compressor 8. The line 7.1 is further connected to the refrigerant tank 1 by a bypass line 9, of a bypass nature, through which a refrigerant can be supplied to the line 7.1 via a bypass expansion valve 10, wherein the temperature of the refrigerant downstream of the bypass valve 10 is -4°C in this embodiment, and the pressure is 30 bar.

The first-stage compressors 7 and second-stage compressors 8 are connected in series with an oil separator 11 with a maximum pressure of 120 bar, from which the refrigerant in gaseous form is directed through line 12 to cooler 13, where the refrigerant in gaseous form is cooled within the pressure range of 120 bar and/or condensed at lower pressure and temperature parameters of the refrigerant resulting from the correspondingly lower temperatures of the coolant of the gas cooler 13. From cooler 13, the refrigerant, mainly in gaseous form, is transferred through line 4.2 of the working medium return with an expansion valve 4.4 to tank 1. The separated oil from the oil separator 11 is directed through oil lines 11.1 and 11.2 to the lubrication systems of the first-stage compressor 7 and the second-stage compressor 8.

The gas cooler 13 is a shell-and-tube heat exchanger, where the medium cooling the circulating refrigerant in the form of carbon dioxide CO2 is sea water, supplied and discharged to and from the cooler 13 via lines 13.1, while the refrigerant flows in the inter-pipe space 13.2 in the cooler jacket 13.

From pipeline 12 to tank 1 through bypass line 14 the medium is supplied in case of too low quantity of medium at the suction of compressors 7, 8. Bypass line 14 is equipped with solenoid valve 14.1 controlled by the automation system. Valve 4.5 on pipeline 4.2 protects valve 4.4 against impact of medium with higher pressure from bypass line 14.

Figure 2 shows an example of an embodiment of a refrigeration device in the form of a unit with a gas cooler unit 13. As shown in this drawing, the unit comprises a number of units constituting, in combination, a refrigeration device according to the invention, installed in this example of an embodiment in a frame 15. The units described above in the description of the cooling system shown in Figure 1 are mounted in the frame 15. Figure 2 shows a refrigerant tank 1 mounted in the frame 15, where carbon dioxide CO2, designated in refrigeration technology as R 744, is collected.

Tank 1 is a vertically arranged drum with bottoms 2, 3. Tank 1 is equipped in the upper bottom 2 with at least one safety valve 16. In this embodiment, Fig. 2 shows two safety valves 16. Also shown is a bypass expansion valve 10 located on the bypass pipeline 9, of a bypass nature. Also shown are compressors 7 and 8. In addition to the aggregate in the form of a set of devices mounted in the frame 15, this drawing also shows a cooler 13, together with a refrigerant inlet pipeline 12 and a refrigerant gas return pipeline 4.2, as well as inlet and outlet nozzles 13.1 for cooling sea water supplied to the set of tubes placed inside the jacket of this gas cooler 13. An example location of the refrigerant filter 17 is also shown.

In the next drawing, Fig. 3 and Fig. 4, an example of an embodiment of a refrigerant tank 1 is shown, respectively, in a half-sectional half-view in Fig. 3 and in a cross-section in Fig. 4. In this example of an embodiment, the vertical tank 1 has the form of a steel sheet drum. The drum is closed at the top and bottom by bottoms 2, 3. Fig. 4 shows a bypass connector 20 for the outlet of the refrigerant in gaseous form from the tank 1 to the compressor 8, and a connector 21 for receiving the refrigerant in liquid form from the tank 1 to the evaporators 5.2 and 6.2.

The drawing Fig. 5 shows a view of a gas cooler 13. Here, the pipe stubs 13.1 of the cooling sea water inlet and outlet to and from the pipe assembly 13.3 shown in the following drawings are visible. The gas cooler 13 is closed on one side by a flange assembly with the sea water inlet and outlet stubs 13.1. On the other side, the gas cooler 13 is closed by standardized flanges and an inspection cap 22.

A cross-section of the gas cooler 13 with a vertical plane, consistent with the longitudinal axis of symmetry of the cooler jacket 13.2 is shown in Figure 6. Here, the sets of flanges and covers closing the cooler 13 on both sides are shown. The cooler 13, whose task is to cool the gaseous carbon dioxide, contains inside the jacket 13.2 a set of tubes in which sea water flows. Inside the jacket 13.2, on the other hand, a gaseous refrigerant in the form of CO2, also designated in refrigeration technology as R 744, flows. The sea water flowing in the set of tubes 13.3 constitutes the cooling agent for the carbon dioxide CO2 flowing in the cooler jacket 13.

Figure 8 shows a cross-section of the jacket 13.2 of the cooler 13, between the flanges closing this jacket 13.2. This figure shows a cross-section of the cooler with a plane perpendicular to the main axis of symmetry of the jacket 13.2, showing the system of tubes 13.3 inside which sea water flows.

The interior of the jacket 13.2 of the cooler 13 is divided in this embodiment by flat longitudinal side shelves 13.7 into two parts connected to each other in the middle: an upper chamber 13.8 and a lower chamber 13.9. The upper chamber 13.8 of the interior of the jacket is supplied with refrigerant from the inlet nozzle, while the lower chamber 13.9 is connected to the discharge nozzle of the refrigerant after it has cooled in the cooler 13.

The above-mentioned sets of tubes 13.4, 13.5 for the flow of sea water are shown in the attached drawings Fig. 8 and Fig. 10. The term upper set of tubes 13.4 should be understood as tubes 13.3 arranged above the horizontal plane C-C, designated in Fig. 8. The term lower set of tubes 13.5 should be understood in such a way that it refers to the lower set of tubes 13.5 arranged below the horizontal plane C-C, designated in this drawing in the zone of the lower chamber 13.9 visible in Fig. 6.

The number and diameter of the tubes are related to each other by the criterion of the seawater flow rate in the tubes 13.3. In the solution according to the invention, the cooling agent in the form of seawater flows in the tubes. The cooling agent in the form of CO2 flows inside the shell 13. The flow rate is crucial for developing turbulent flow and obtaining the highest possible heat exchange coefficients in the shell-and-tube exchanger. Both parameters are related to the length and configuration of the tubes 13.4, 13.5, which affects the size of the heat exchange surface. By selecting these parameters in the form of the number, diameter and configuration of the tubes 13.4, 13.5, it is possible to obtain the expected heat exchange surface. The size of the free surface between the tubes is also important for the degree of heat exchange, which affects the efficiency of the flow of the cooling agent CO2 inside the shell 13. A large distance between the tubes 13.4, 13.5 reduces the turbulence of the CO2 flow, which slows down the cooling process. However, this facilitates inspection and cleaning of the space between the tubes.

The recommended distance between the seawater flow tubes inside the cooler casing 13.2, in this embodiment, is at least 6 mm and an additional 6 mm if there is a need to clean the space between the tubes. These data may be different in other embodiments and are dependent on the dimensions of the individual components of the cooler 13. In this embodiment, the tubes 13.3 and the sieve bottoms between which these tubes are attached are made of titanium. The connections of the tubes to the sieve plate are welded.

In the embodiment shown in the drawing from Fig. 5 to Fig. 9, the tubes 13.4 and 13.5, fixed between the sieve bottoms 13.6, and stabilized by transverse sieve plates, allow the CO2 coolant to be guided through the space inside the jacket 13.2 of the gas cooler. The coolant guided by the tube assemblies 13.4, 13.5 in this embodiment is sea water, which is drawn in a known manner from the body of water in which the ship is currently located.

As mentioned above, the tubes conducting sea water as a cooling medium for the refrigerant are grouped into two units visible in the drawing fig. 8: an upper tube unit 13.4 and a lower tube unit 13.5. In this embodiment, these two tube units 13.4 and 13.5 are connected with each other in a flow manner inside the casing 13.2. The upper unit 13.4 is located in the zone of the above-mentioned upper chamber 13.8, while the lower unit 13.5 is located in the zone of the above-mentioned lower chamber 13.9, separated in the drawing fig. 8 by a horizontal plane C-C. This is shown in the drawings fig. 6, fig. 8 and fig. 10. The tube units 13.4, 13.5 are mounted in the tube sheets 13.6. This is shown in Figure 6. At the same time, a refrigerant in the form of a gas-liquid mixture of carbon dioxide CO2 flows countercurrently through spaces 13.8, 13.9 inside the jacket 13.2 of the cooler 13. As a result of cooling inside the jacket 13.2 of the cooler 13, the mixture is cooled and the liquid phase of CO2 partially condenses.

Figures 8 and 10 show the grouping of the coolant flow tubes in the form of sea water in the tube assemblies: upper 13.4 and lower 13.5. In the upper assembly 13.4, four tubes are arranged symmetrically one next to the other, as the first layer. On this first layer of four tubes, a second layer of four tubes is arranged symmetrically so that there is a middle gap between both pairs of tubes of the second layer. On the inner tubes of the second layer of tubes, a third layer is also arranged symmetrically, in the form of a pair of tubes. The upper assembly 13.4 of the coolant flow tubes in the cooler 13 therefore contains 10 tubes for the coolant flow in the form of sea water supplied to this cooler.

The same lower assembly 13.5 of pipes conducting the coolant in the form of sea water is located under the plane C-C shown in drawings fig. 8 and fig. 10 theoretically dividing the interior of the jacket 13.2 of the cooler 13 into an upper chamber 13.8 and a lower chamber 13.9. The pipes 13.3 are supplied with the coolant in the form of sea water. This is shown in drawings fig. 6 and fig. 10. Here too, in the second chamber 13.9 shown in drawing fig. 6, on the first layer of four pipes is arranged a second, symmetrical layer of four pipes, where between two pairs of pipes in this second layer a central distance is maintained. Similarly to the upper assembly, on this second layer is arranged a third layer in the form of two pipes.

Both units 13.4, 13.5 of the refrigerant guide tubes therefore contain a central channel 23. This is shown in Fig. 8. The cooling agent in the form of carbon dioxide CO2 supplied to and discharged from the cooler jacket 13.2 can flow both on the outside of the given unit of tubes and inside this unit in the described channel 23, cooling the refrigerant CO2 flowing inside the jacket 13.2 of the cooler 13. The described organization of the units 13.4, 13.5 of the refrigerant CO2 cooling tubes, in countercurrent to the seawater flow, made it possible to additionally lower the temperature of the refrigerant CO2 at the inlet to the high-pressure expansion valve, and finally lower the temperature of the refrigerant supplied in the circuit to the tank 1. The described structure of the arrangement of the seawater flow tubes 13.3 is exemplary and a different internal structure of the cooler 13 is not excluded.

In this embodiment, the cooler shell 13 has an outside diameter of 150 mm, while the internal tubes for guiding the sea water have an outside diameter of 16 mm and are made of titanium, as are the tube sheets 13.6, in which the tubes 13.3 are welded. Thanks to the use of titanium, the tubes 13.3 and the tube sheets 13.6 are resistant to corrosion caused by sea water. In this embodiment, the cooler 13 has a total length of 1738 mm, together with the sea water inlet and outlet nozzles and the inspection cap 22.

The refrigerant in the form of carbon dioxide, referred to in refrigeration technology as R744, in the form of a two-phase liquid-gas mixture is collected in the tank 1, and then through a copper liquid pipeline 4.1 is led to the expansion valves 5.1 and 6.1 located in the freezing chambers 5 and cooling chamber 6. There is also a dehydration filter 4.3 on the liquid pipeline 4.1, which filters the agent from impurities and moisture. Electronically controlled expansion valves 5.1, 6.1 in the freezing chamber 5 and in the cooling chamber 6 cause a drop in the pressure of the refrigerant, which results in a decrease in the boiling point of the agent, its rapid evaporation in the evaporators of chambers 5, 6. As a result of their operation, the temperature in chambers 5, 6 drops to a set level. In this example of implementation, in the freezing chamber to a temperature of 20°C, while in the cooling chamber to a temperature of +4°C.

The first-stage compressor 7, also designated LT in Fig. 1, sucks the medium from the outlet pipeline 5.3 of the freezing chamber 5 and the evaporator 5.2 and compresses it into the pipeline 7.1. The second-stage compressor 8, also designated in Fig. 1 as MT, sucks off the refrigerant pumped by the first-stage compressor 7 from the evaporator 5.2, the refrigerant from the outlet pipeline 6.3 from the cooling chamber 6 and evaporator 6.2, and the refrigerant from the bypass pipeline 9. The refrigerant is pumped into the bypass pipeline 9 from the tank 1 through the bypass expansion valve 10 as a result of the pressure difference in the tank 1 and in the pipeline 9. The second-stage compressor 8 pumps the refrigerant to the oil separator 11 which separates the refrigerant from the oil, which is returned through lines 11.1 and 11.2 to the lubrication system of the aforementioned compressors 7, 8.

The R744 refrigerant in the form of carbon dioxide is pumped into the cooler 13 via the pipeline 12. The refrigerant is cooled and/or condensed in the cooler 13. Heat exchange takes place between the hot refrigerant conducted in the cooler jacket and the lower temperature seawater pumped through the seawater flow tubes 13.3 in the cooler 13. The seawater is supplied and released in a known manner via the pipeline via the nozzles 13.1.

The cooled refrigerant is transported through line 4.2 to tank 1. Upstream of tank 1, on line 4.2, there is a high-pressure expansion valve 4.4, which reduces the pressure of the refrigerant to the condensing pressure in separator 1. The liquid from separator 1 is collected through line 4.3 and evaporated in evaporators 5.2, 6.2, as described above.

A high-pressure medium is supplied to the tank 1 via the bypass pipeline 14 in case there is a shortage of this medium at the suction of the compressor 7 or 8. The bypass pipeline 14 is equipped with a bypass valve 14.1 controlled by a known automatic system.

List of symbols in the drawing.

1. Refrigerant tank

2. Upper bottom

3. Bottom bottom

4.1. Liquid refrigerant pipeline

4.2. Gas refrigerant pipeline

4.3. Drain filter

4.4. High pressure expansion valve

4.5. Check valve

5. Freezing chamber

5.1 Expansion valve

5.2 Freezing chamber evaporator

5.3 Gas medium pipeline from the freezing chamber

6. Cooling chamber

6.1. Expansion valve

6.2. Refrigeration chamber evaporator

6.3. Gas medium pipeline from the cooling chamber

7. First stage compressor

7.1 Discharge-suction pipeline between compressors

8. Second stage compressor

9. Bypass pipeline

10. Bypass expansion valve

11. Oil separator

11.1. Oil pipeline

11.2. Oil pipeline

12. Refrigerant inlet pipe

13. Gas cooler

13.1. Seawater pipeline

13.2. Radiator jacket

13.3. Seawater flow tubes

13.4. Upper Tube Assembly

13.5. Lower Tube Assembly

13.6. Sieve bottom

13.7. Side shelf

13.8. Upper chamber

13.9. Lower chamber

14. Bypass pipeline

14.1. Bypass solenoid valve

15. Frame

16. Safety valve

17. Refrigerant filter

18. Speculum

19. Tank base

20. Bypass connector

21. Liquid refrigerant collection port

22. Hubcap.

23. Internal channel.

Claims (8)

1. A cooling system, especially on a marine unit, comprising a tank (1) for a refrigerant in the form of carbon dioxide CO2, connected via an expansion valve (5.1) to an evaporator (5.2) in a freezing chamber (5) and via an expansion valve (6.1) to an evaporator (6.2) in a cooling chamber (6), wherein the outlet of the evaporator (5.2) in the freezing chamber (5) and the outlet of the evaporator (6.2) in the cooling chamber (6) are connected to the first and second stage compressors (7, 8) and to the refrigerant tank (1), and the outlet of the refrigerant in the form of carbon dioxide CO2 from the second stage compressor (8) is connected via an oil separator (11) to the inlet of said refrigerant to the gas cooler (13), while the outlet of the refrigerant from the gas cooler (13) is connected via a high-pressure expansion valve (4.4) to the inlet of said refrigerant to the refrigerant tank (1), wherein the refrigerant outlet from the first-stage compressor (7) and the refrigerant inlet to the second-stage compressor (8) are connected, via a bypass expansion valve (10), to the refrigerant tank (1), characterized in that the refrigerant outlet from the oil separator (11) to the gas cooler (13) is connected to the refrigerant tank (1) via a bypass solenoid valve (14.1), and the gas cooler outlet from the gas cooler (13) to the refrigerant tank (1) is equipped with a non-return valve (4.5), wherein the gas cooler (13) is supplied with a refrigerant in the form of sea water. 2. A cooling system according to claim 1, characterized in that the bypass solenoid valve (14.1) is controlled by the suction pressure difference between the compressor (7) of the first compression stage and the compressor (8) of the second compression stage. 3. A cooling system according to claim 1 or 2, characterized in that the liquid refrigerant outlet from the tank (1) is connected to the expansion valves (5.1, 6.1) of the freezing chamber (5) and the cooling chamber (6) via a dehydration filter (4.3). 4. A cooling system according to claim 1 or 2, characterized in that the outlet (5.3) of the refrigerant from the evaporator (5.2) of the freezing chamber (5) is connected to the suction inlet of the first-stage compressor (7), the pressure outlet of which is connected to the outlet of the refrigerant from the evaporator (6.2) of the freezing chamber (6) and to the inlet to the second-stage compressor (8) and, via the oil separator (11) and the gas cooler (13), to the inlet to the refrigerant tank (1). 5. A refrigeration device, especially on a marine unit, comprising a tank (1) for a refrigerant in the form of carbon dioxide CO2, mounted in a frame (15), connected by a pipeline (4.1) through an expansion valve (5.1) to an evaporator (5.2) in a freezing chamber (5) and in parallel through an expansion valve (6.1) to an evaporator (6.2) in a cooling chamber (6), where the pipeline (5.3) of the outlet from the evaporator (5.2) in the freezing chamber (5), and the pipeline (6.3) of the outlet from the evaporator (6.2) in the cooling chamber (6) are connected to the first and second stage compressors (7, 8) and are connected by a pressure-suction pipeline (7.1, 10) to the refrigerant tank (1), while the refrigerant outlet from the compressor (8) of the second compression stage is connected by a branch pipeline (12) to the refrigerant inlet stub pipe to the gas cooler (13), and the outlet of the refrigerant from the cooler (13) is connected by a refrigerant pipeline (4.2) via a high-pressure expansion valve (4.4) with the inlet of this working medium to the refrigerant tank (1), wherein the outlet of the pressure-suction pipeline (7.1) of the refrigerant from the first-stage compressor (7) and the inlet of the refrigerant to the second-stage compressor (8) are connected by a bypass line (9) via a bypass expansion valve (10) with the refrigerant tank (1), PL 246608 Β1 characterized in that the refrigerant pipeline (12) from the oil separator (11) to the gas cooler (13) is connected by a bypass pipeline (14) to the refrigerant tank (1), wherein the bypass pipeline (14) is equipped with an electromagnetic valve (14.1), and the gas cooler return pipeline (4.2) from the gas cooler (13) to the refrigerant tank (1) is equipped with a non-return valve (4.5), wherein the gas cooler (13) is supplied with a refrigerant in the form of sea water. 6. A refrigeration device according to claim 5, characterized in that the solenoid valve (14.1) is controlled by the suction pressure difference between the compressor (7) of the first compression stage and the compressor of the second compression stage (8). 7. A refrigeration device according to claim 4, characterized in that the sea water tube assembly (13.3) and the tube sheets (13.6) of the gas cooler (13) are made of titanium. 8. A refrigeration device according to claim 3, characterized in that the liquid refrigerant outlet pipeline (4.1) from the tank (1) is connected to the expansion valves (5.1) of the freezing chamber (5) and (6.1) of the cooling chamber (6) via a dehydration filter (4.3).