Cooling system

Abstract

This invention provides a cooling system that enables the use of substances not previously used in conventional refrigeration systems as refrigerants in the thermal cycle, or expands the range of substances that can be used as refrigerants in the thermal cycle. [Solution] The system includes a sealed container 10 for storing liquid refrigerant, which includes a first outlet 11 and an inlet 13; a pressure reducing device 20 connected to the first outlet 11 that adjusts the pressure inside the sealed container 10 to a pressure lower than atmospheric pressure by sucking gas from the sealed container 10 through the first outlet 11; and a refrigerant circulation device 30 which includes a refrigerant flow path 31 connected to the pressure reducing device 20 and the inlet 13, and causes the liquid refrigerant, which is the liquefied gas sucked from the sealed container 10 by the pressure reducing device 20, to flow into the sealed container 10 through the inlet 13.

Description

Technical Field

[0005] , , ,

[0006]

[0001] Embodiments of the present invention relate to a cooling system that utilizes the temperature drop of a refrigerant due to decompression.

Background Art

[0007] On the other hand, as cooling devices that do not use a compressor, boiling cooling devices such as those disclosed in JP2011-142298A, WO2017 / 119113A1, and JP2021-162195A are known.

[0008] Boiling cooling systems efficiently cool a temperature-controlled object by exchanging heat between the liquid and the object, thereby utilizing latent heat absorption during the vaporization process. While a pump is typically required to circulate the liquid or its vaporized form, it requires little to no lubrication. Furthermore, the pump's energy consumption is relatively low. Therefore, boiling cooling systems are considered environmentally friendly devices.

[0009] However, with boiling cooling systems, the temperature of the circulating liquid is usually near its boiling point at atmospheric pressure, making it impossible to cool at temperatures significantly below 0°C, for example. This severely restricts the cooling temperature and the temperature-controlled object. Therefore, it is difficult to ensure high refrigeration capacity at low or very low temperatures using boiling cooling systems. [Overview of the project]

[0010] In recent years, while the development of HFO-based refrigerants has progressed as mentioned above, the development of antifreezes with a low environmental impact has also progressed. As a result, HFO-based solvents that have a low GWP and are non-flammable and can be used as antifreeze have been put into practical use. Such solvents have a boiling point of, for example, 70°C or higher at atmospheric pressure, making them unsuitable for vapor compression type refrigeration systems. However, if a thermal cycle can be realized using such HFO-based solvents, it may be possible to realize a cooling system that can ensure the currently strongly desired low environmental impact, high safety, and high refrigeration capacity.

[0011] Therefore, the inventors of this invention diligently conducted research to realize a novel cooling system that can use HFO-based solvents, such as those mentioned above, as refrigerants in a thermal cycle. More generally, they diligently conducted research to realize a novel cooling system that can shift the range of substances that can be used as refrigerants in a thermal cycle from a range different from that which can be used in vapor compression type refrigeration systems. They discovered that the above cooling system can be realized by a structure that cools the refrigerant by lowering its temperature through reduced pressure, and then releases the heat absorbed by the refrigerant under atmospheric pressure, and thus conceived the present invention.

[0012] In other words, the object of the present invention is to provide a cooling system that enables the use of substances that have not been used in conventional refrigeration methods as refrigerants in a thermal cycle, or that expands the range of substances that can be used as refrigerants in a thermal cycle.

[0013] One embodiment of the present invention relates to the following embodiments "1" to "18".

[0014] [1] A container for storing liquid refrigerant, including an outlet and an inlet, A pressure reducing device connected to the outlet, which adjusts the pressure inside the container to a pressure lower than atmospheric pressure by drawing gas from the container through the outlet, A refrigerant circulation device is provided, which includes a refrigerant flow path connected to the pressure reducing device and the inlet, and which causes the liquid refrigerant liquefied from the gas drawn from the container by the pressure reducing device to flow into the container through the inlet, A cooling system that cools a temperature-controlled object using the refrigerant in the container.

[0015] [2] The pressure reducing device is A gas flow path connected to the outlet, A gas suction pump is provided in the gas flow path and draws the gas from the container into the gas flow path, It includes a reservoir tank connected to the gas flow path and storing the gas flowing out of the gas flow path and / or the liquid refrigerant liquefied from the gas, The cooling system according to [1], wherein the refrigerant flow path is connected to the reservoir tank.

[0016] [3] The cooling system according to [2], wherein the pressure in the reservoir tank is higher than the pressure in the container, and the reservoir tank liquefies at least a portion of the gas flowing out of the gas passage into liquid refrigerant and stores the liquid refrigerant.

[0017] [4] The cooling system according to [2] or [3], wherein the refrigerant circulation device further includes a circulation pump provided in the refrigerant flow path for drawing liquid refrigerant from the reservoir tank into the refrigerant flow path.

[0018] [5] The cooling system according to any one of [2] to [4], wherein the depressurizing device further includes a cooling section for cooling the portion of the gas flow path downstream of the gas suction pump and / or the reservoir tank.

[0019] [6] The refrigerant circulation device further includes a buffer container provided in the refrigerant flow path so as to form a part of the refrigerant flow path and for storing the liquid refrigerant, The liquid refrigerant drawn from the reservoir tank into the refrigerant flow path flows into the container after passing through the buffer container, the cooling system according to any one of [2] to [5].

[0020] [7] Further comprising a heat exchanger connected to the refrigerant flow path and cooling the liquid refrigerant flowing through the refrigerant flow path, The buffer container is provided in a portion upstream of the portion where the heat exchanger in the refrigerant flow path is connected, the cooling system according to [6].

[0021] [8] The reservoir tank is disposed above the buffer container, the cooling system according to [6] or [7].

[0022] [9] The gas suction pump is configured to suck the gas by the rotation of the motor, The gas suction pump adjusts the rotational speed of the motor according to the temperature inside the container, the pressure inside the container, the temperature of the heat medium cooled by the refrigerant, or the temperature of the temperature control target, the cooling system according to any one of [2] to [8].

[0023]

[10] A flow control valve for controlling the flow rate of the gas flowing through the gas flow path by adjusting the opening degree is provided in a portion upstream or downstream of the gas suction pump in the gas flow path, The flow control valve adjusts its opening degree according to the temperature inside the container, the pressure inside the container, the temperature of the heat medium cooled by the refrigerant, or the temperature of the temperature control target, the cooling system according to any one of [2] to [9].

[0024]

[11] Further comprising a gas supply device for supplying gas into the container, The gas supply device adjusts the amount of the gas supplied into the container according to the temperature inside the container, the pressure inside the container, the temperature of the heat medium cooled by the refrigerant, or the temperature of the temperature control target, the cooling system according to any one of [2] to

[10] .

[0025]

[12] Further provided with a heat exchanger that is connected to the refrigerant flow path and cools the liquid refrigerant flowing through the refrigerant flow path. The refrigerant circulation device is provided at a portion downstream of the portion of the refrigerant flow path to which the heat exchanger is connected, and includes a three-way valve including a first port, a second port, and a third port. The three-way valve is capable of adjusting the flow rate of the refrigerant flowing into the first port and flowing out from the second port, and the flow rate of the refrigerant flowing into the first port and flowing out from the third port. The three-way valve constitutes a part of the refrigerant flow path in the flow path between the first port and the second port. The cooling system according to any one of [1] to

[11] , wherein the third port and a portion of the refrigerant flow path upstream of the portion to which the heat exchanger is connected are connected by a bypass flow path.

[0026]

[13] When the liquid level height of the refrigerant in the container exceeds a predetermined height, the three-way valve reduces the flow rate of the refrigerant flowing into the first port and flowing out from the second port, and increases the flow rate of the refrigerant flowing into the first port and flowing out from the third port. The cooling system according to

[12] , wherein when the liquid level height of the liquid refrigerant in the container is below a predetermined height, the three-way valve increases the flow rate of the refrigerant flowing into the first port and flowing out from the second port, and decreases the flow rate of the refrigerant flowing into the first port and flowing out from the third port.

[0027]

[14] When the liquid level height of the liquid refrigerant in the container exceeds a predetermined height, the three-way valve blocks the flow of the refrigerant flowing into the first port and flowing out from the second port. Allows the flow of the refrigerant flowing into the first port and flowing out from the third port. The cooling system according to

[12] , wherein when the liquid level height of the liquid refrigerant in the container is below a predetermined height, the three-way valve allows the flow of the refrigerant flowing into the first port and flowing out from the second port, and blocks the flow of the refrigerant flowing into the first port and flowing out from the third port.

[0028]

[15] Further comprising a heat transfer device including a heat transfer channel for passing a heat transfer medium, The heat transfer fluid channel is arranged within the container and includes a heat exchange section that exchanges heat between the heat transfer fluid and the refrigerant. The cooling system according to any one of [1] to

[14] , wherein the heat transfer medium channel sends the heat transfer medium from outside the container to the heat exchange section, and sends the heat transfer medium that has undergone heat exchange in the heat exchange section to outside the container.

[0029]

[16] The cooling system according to any one of [1] to

[15] , wherein the refrigerant is a substance whose boiling point at atmospheric pressure is 30°C or higher.

[0030]

[17] The cooling system according to any one of [1] to

[16] , wherein the refrigerant has a GWP of 10 or less.

[0031]

[18] The cooling system according to any one of [1] to

[17] , wherein the refrigerant is HFO-1336mzz-Z.

[0032] According to the present invention, it becomes possible to use substances that were not used in conventional refrigeration systems as refrigerants in thermal cycles, or to expand the range of substances that can be used as refrigerants in thermal cycles. [Brief explanation of the drawing]

[0033] [Figure 1] This figure schematically shows a cooling system according to the first embodiment. [Figure 2] Figure 1 is a block diagram showing the functional configuration of the controllers that make up the cooling system. [Figure 3] Figure 1 shows a pH diagram of an example of a refrigerant used in a cooling system. [Figure 4] This figure schematically shows a cooling system according to the second embodiment. [Figure 5] This figure schematically shows a cooling system according to the third embodiment. [Figure 6] This figure schematically shows a cooling system according to the fourth embodiment. [Modes for carrying out the invention]

[0034] The following describes each embodiment.

[0035] <First Embodiment> Figure 1 is a schematic diagram of the cooling system S1 according to the first embodiment. First, the configuration of the cooling system S1 will be described.

[0036] (Cooling system configuration) As shown in Figure 1, the cooling system S1 according to the first embodiment includes a sealed container 10, a pressure reducing device 20, a refrigerant circulation device 30, a heat exchanger 40, a heat transfer medium flow device 50, a gas supply device 60, and a controller 100.

[0037] In the cooling system S1, liquid refrigerant is stored in a sealed container 10. The pressure reducing device 20 is connected to the sealed container 10 and reduces the pressure inside the sealed container 10 by sucking in gas present in the sealed container 10 or gas that has vaporized inside the sealed container 10. The refrigerant circulation device 30 is connected to the pressure reducing device 20 and passes the liquid refrigerant, which has liquefied from the gas sucked in by the pressure reducing device 20 from the sealed container 10, through the device, allowing it to flow back into the sealed container 10. The refrigerant circulation device 30 is also connected to a heat exchanger 40 outside the sealed container 10. As a result, the refrigerant passed through the refrigerant circulation device 30 circulates between the sealed container 10 and the heat exchanger 40. The cooling system S1 then cools the heat transfer medium passed through the heat transfer medium circulating device 50 inside the sealed container 10, and the heat transfer medium circulating device 50 sends the cooled heat transfer medium to the temperature-controlled object T. Furthermore, the refrigerant circulation device 30 releases the heat absorbed by the refrigerant from the heat transfer medium through the heat exchanger 40. In addition, in this embodiment, the pressure reducing device 20 also releases heat from the cooling unit 25, which will be described later. As a result, the heat transfer medium is continuously cooled.

[0038] In the cooling system S1, as described later, the pressure inside the sealed container 10 is reduced to a pressure lower than atmospheric pressure by the pressure reducing device 20. On the other hand, the refrigerant flow environment in the refrigerant circulation device 30 and the refrigerant flow environment in the heat exchanger 40, which are outside the sealed container 10, are set to a pressure higher than the pressure inside the sealed container 10, for example, to atmospheric pressure. In such an environment, when refrigerant flows from the heat exchanger 40 into the sealed container 10, the refrigerant expands, and the temperature of the refrigerant decreases inside the sealed container 10. As a result, the heat transfer medium can be cooled by the refrigerant that has been cooled inside the sealed container 10. At this time, the refrigerant evaporates through heat exchange with the heat transfer medium, and in this case, the heat transfer medium can be efficiently cooled by the latent heat of vaporization of the refrigerant. The evaporated refrigerant is then in a gaseous state and is sucked in by the pressure reducing device 20.

[0039] The refrigerant circulated by the refrigerant circulation device 30 is not particularly limited, but is, for example, a substance that is liquid at atmospheric pressure and a standard ambient temperature (e.g., 25°C), and which, when expanded in an environment of, for example, 0.1 atmospheres, becomes -5°C or lower, and preferably a substance that, when expanded in an environment of 0.01 atmospheres, becomes -30°C or lower. When such a substance is used as a refrigerant, cooling down to low temperatures becomes possible. In this specification, atmospheric pressure means 1 atmosphere, or in other words, 0.1 MPa (Abs). The parts of the cooling system S1 will be described in detail below.

[0040] The sealed container 10 includes a first outlet 11, a second outlet 12, an inlet 13, a gas receiving inlet 14, a heat transfer medium inlet 15, and a heat transfer medium outlet 16, and is a container that prevents the outflow and leakage of gas and liquid from parts other than these openings (11-16). The sealed container 10 is constructed in a way that it can maintain its shape when the internal pressure is reduced, and is a so-called vacuum insulated container.

[0041] Maintaining the shape of the sealed container 10 during depressurization depends on the internal pressure being reduced, but for example, when the pressure is reduced to 0.1 atmospheres, it is preferable that the outer shell of the sealed container 10 be made of a thick, hard metal or the like. However, the specific structure of the sealed container 10 is not particularly limited and can be appropriately determined according to the degree of depressurization planned. The sealed container 10 may also consist of a container body with an opening and a lid that opens and closes the opening. In this case, it is necessary to ensure sufficient airtightness and sealing when the lid is closed.

[0042] The sealed container 10 is designed to store liquid refrigerant, where the symbol Lf indicates the liquid reservoir of the refrigerant, and the symbol Gf indicates the gas phase portion. In other words, in this embodiment, the sealed container 10 stores liquid refrigerant while forming a gas phase portion Gf. The pressure reducing device 20, described later, reduces the pressure inside the sealed container 10 by sucking in the gas inside the sealed container 10. When the gas phase portion Gf is formed, liquid refrigerant is prevented from entering the pressure reducing device 20, and the operating state of the pressure reducing device 20 can be stabilized. Furthermore, failure of the pressure reducing device 20 can be suppressed.

[0043] An environment in which liquid refrigerant and gaseous portion Gf coexist within the sealed container 10 can be created by controlling the operation of the pressure reducing device 20, refrigerant circulation device 30, and gas supply device 60.

[0044] The first outlet 11 is connected to the depressurization device 20 and is an opening intended to release gas. Therefore, it is preferable that it opens in the gas phase portion Gf of the sealed container. The gas inlet 14 is connected to the gas supply device 60 as described later, and like the first outlet 11, it is preferable that this gas inlet 14 also opens in the gas phase portion Gf of the sealed container 10. The first outlet 11 and the gas inlet 14 are preferably provided on the upper part of the upper wall or side wall of the sealed container 10. In the illustrated example, the first outlet 11 and the gas inlet 14 are formed on the upper wall of the sealed container 10.

[0045] The second outlet 12 is an opening for discharging the liquid refrigerant from the sealed container 10. The inlet 13 is an opening for receiving the liquid refrigerant that the refrigerant circulation device 30 will pass through. The second outlet 12 and the inlet 13 preferably open to the liquid phase portion of the sealed container 10, and are preferably located at the bottom of the bottom wall or side wall of the sealed container 10. In the illustrated example, the second outlet 12 is formed in the bottom wall of the sealed container 10, and the inlet 13 is formed below the midpoint in the vertical direction of the side wall of the sealed container 10. In addition, the heat transfer medium inlet 15 and the heat transfer medium outlet 16 preferably open to the liquid phase portion of the sealed container 10, and in the illustrated example, the heat transfer medium inlet 15 and the heat transfer medium outlet 16 are formed in the bottom wall of the sealed container 10.

[0046] The pressure reducing device 20 is connected to the first outlet 11 and adjusts the pressure inside the sealed container 10 to a pressure lower than atmospheric pressure by sucking gas from the sealed container 10 through the first outlet 11. More specifically, the pressure reducing device 20 in this embodiment includes a gas flow path 21 connected to the first outlet 11, a gas suction pump 22 provided on the gas flow path 21 for sucking gas from the sealed container 10 into the gas flow path 21, and a reservoir tank 23 connected to the downstream end 21B of the gas flow path 21 for storing the gas flowing out from the downstream end 21B.

[0047] The gas flow path 21 includes an upstream end 21A connected to the first outlet 11 and a downstream end 21B connected to the reservoir tank 23. The gas suction pump 22 is located in the portion of the gas flow path 21 between the upstream end 21A and the downstream end 21B.

[0048] The type of gas suction pump 22 is not particularly limited, but it is preferable that it be a dry vacuum pump in which lubricating oil does not flow out or flows out very little to the suction path (gas flow path 21). The dry vacuum pump may be a diaphragm type dry vacuum pump, an oscillating piston type dry vacuum pump, a rotary vane type dry vacuum pump, a scroll type dry vacuum pump, etc., and may be different from the methods exemplified above. However, the gas suction pump 22 may also be a wet vacuum pump.

[0049] In this embodiment, the gas suction pump 22 is a dry vacuum pump. The gas suction pump 22 includes a motor 22M controlled by an inverter, such as an AC motor or a brushless DC motor. The gas suction pump 22 can adjust the amount of gas suctioned by adjusting the rotational speed of the motor 22M, thereby adjusting the pressure inside the sealed container 10. The rotational speed of the motor 22M is adjusted by adjusting the frequency of the AC current supplied to the motor 22M using an inverter (not shown).

[0050] Furthermore, in this embodiment, a flow control valve 24 is provided in the gas flow path 21, and the pressure inside the sealed container 10 can also be adjusted by adjusting the opening degree of the flow control valve 24. By adjusting the opening degree of the flow control valve 24, the flow rate of gas flowing through the gas flow path 21 can be adjusted. As a result, the amount of gas drawn in is adjusted, and thus the pressure inside the sealed container 10 can be adjusted.

[0051] The gas suction pump 22 and the flow control valve 24 may operate simultaneously to regulate the pressure inside the sealed container 10. Alternatively, the operating state of the gas suction pump 22 may be kept constant and the opening degree of the flow control valve 24 may be adjusted, or the opening degree of the flow control valve 24 may be kept constant and the operating state of the gas suction pump 22 may be controlled.

[0052] In this embodiment, the flow control valve 24 is provided in the upstream portion of the gas flow path 21 relative to the gas suction pump 22, but it may also be provided in the downstream portion of the gas suction pump 22. The flow control valve 24 is composed of, for example, a butterfly valve, but is not particularly limited.

[0053] The gas suction pump 22 and the flow control valve 24 are electrically connected to and controlled by the controller 100. In this embodiment, the gas suction pump 22 is electrically connected to the controller 100 via an inverter (not shown). The flow control valve 24 may be a valve whose opening degree is adjusted by an electric motor, such as a stepping motor or a servo motor. In this case, the controller 100 is electrically connected to the electric motor. The flow control valve 24 may also be an electromagnetic proportional valve or the like.

[0054] The pressure inside the reservoir tank 23 is higher than the pressure inside the sealed container 10, and is set to, for example, atmospheric pressure. This allows the reservoir tank 23 to liquefy at least a portion of the gas flowing out from the downstream end 21B of the gas flow path 21 into liquid refrigerant, making it easier to store liquid refrigerant. The reservoir tank 23 may have, for example, an openable lid to reduce the power consumption of the gas suction pump 22 when the pressure rises, for safety reasons, and for filling or replenishing refrigerant. That is, the reservoir tank 23 may comprise a container body with an opening and a lid that opens and closes the opening. In this case, it is necessary to ensure sufficient airtightness and sealing when the lid is closed.

[0055] In this embodiment, the depressurization device 20 further includes a cooling unit 25 that cools the portion of the gas flow path 21 downstream of the gas suction pump 22. This promotes the liquefaction of the gas flowing out from the downstream end 21B of the gas flow path 21, and can suppress, for example, the pressure rise in the reservoir tank 23. The cooling unit 25 is composed of, for example, a cooling fan. However, the configuration of the cooling unit 25 is not particularly limited and may be a heat exchanger or the like. The cooling unit 25 may also cool the reservoir tank 23. In this case, the cooling unit 25 may cool the inside of the reservoir tank 23 or the outside of it.

[0056] The refrigerant circulation device 30 includes a refrigerant flow path 31 connected to the pressure reducing device 20 and the inlet 13, and a circulation pump 32 provided in the refrigerant flow path 31 that draws liquid refrigerant from the reservoir tank 23 into the refrigerant flow path 31. Specifically, the refrigerant flow path 31 is connected to the reservoir tank 23 in the pressure reducing device 20. The refrigerant circulation device 30 circulates the liquid refrigerant received from the reservoir tank 23 and allows it to flow into the sealed container 10 from the inlet 13.

[0057] Furthermore, the refrigerant circulation device 30 in this embodiment further includes a buffer container 33 and a three-way valve 34 provided in the refrigerant flow path 31. In this embodiment, the circulation pump 32, buffer container 33, and three-way valve 34 are provided in the refrigerant flow path 31 so as to each constitute a part of the refrigerant flow path 31. The circulation pump 32 is located downstream of the buffer container 33, and the three-way valve 34 is located downstream of the circulation pump 32, but this arrangement is not particularly limited.

[0058] The refrigerant flow path 31 includes an upstream end 31A connected to the reservoir tank 23 and a downstream end 31B connected to the inlet 13. The upstream end 31A is connected to the bottom wall of the reservoir tank 23 and communicates with the reservoir tank 23. The circulation pump 32, buffer container 33, and three-way valve 34 are each provided in the portion of the refrigerant flow path 31 between the upstream end 31A and the downstream end 31B.

[0059] The type of circulation pump 32 is not particularly limited; it may be a non-positive displacement pump or a positive displacement pump. The circulation pump 32 includes a motor 32M controlled by an inverter, such as an AC motor or a brushless DC motor. The circulation pump 32 can adjust the amount of liquid drawn in and thus the flow rate of refrigerant flowing through the refrigerant passage 31 by adjusting the rotational speed of the motor 32M. The rotational speed of the motor 32M is adjusted by adjusting the frequency of the AC current supplied to the motor 32M using an inverter (not shown).

[0060] Furthermore, as the refrigerant passes through the circulation pump 32, its pressure increases. When the refrigerant's pressure increases, its temperature rises. The heat exchanger 40 described above is connected to the refrigerant flow path 31, but the heat exchanger 40 is connected to the refrigerant flow path 31 downstream of the circulation pump 32. This allows the heat exchanger 40 to efficiently cool the refrigerant.

[0061] The buffer container 33 includes an inlet 33A for receiving refrigerant drawn in from the reservoir tank 23 and an outlet 33B for releasing the refrigerant. As a result, the liquid refrigerant drawn in from the reservoir tank 23 into the refrigerant flow path 31 passes through the buffer container 33 from the inlet 33A to the outlet 33B before flowing into the sealed container 10.

[0062] The buffer container 33 is designed to store a certain amount of liquid refrigerant, and in this embodiment, the buffer container 33 stores liquid refrigerant so that its storage space is filled. The storage space of the buffer container 33 does not necessarily have to be filled with liquid refrigerant. However, the larger the amount of liquid refrigerant occupying the storage space of the buffer container 33, the smoother the refrigerant can be discharged from the outlet 33B. From this viewpoint, it is preferable that the storage space of the buffer container 33 be filled with liquid refrigerant, but even if this is not the case, the amount of liquid refrigerant stored in the storage space of the buffer container 33 should be 50% or more in volume ratio to the storage space, and may be 70% or more, 80% or more, or 90% or more.

[0063] In this embodiment, the outlet 33B is provided at the lower part of the side wall of the buffer container 33. This allows the refrigerant to pass through the buffer container 33 smoothly.

[0064] The buffer container 33 receives liquid refrigerant from the inlet 33A. In this embodiment, the reservoir tank 23 is positioned above the buffer container 33, allowing the liquid refrigerant stored in the reservoir tank 23 to be smoothly delivered to the buffer container 33 by its own weight. The inlet 33A is provided on the upper part of the buffer container 33, specifically on the upper wall, thereby reducing the length of the piping between the reservoir tank 23 and the buffer container 33 in the refrigerant flow path 31.

[0065] The buffer container 33 primarily accepts liquid refrigerant from the inlet 33A, but it may also accept gas containing unliquefied vaporized refrigerant. Here, the liquid refrigerant or gas accepted into the buffer container 33 may be at a relatively high temperature. However, when liquid refrigerant or gas from the reservoir tank 23 flows into the buffer container 33 that stores the liquid refrigerant, unwanted disturbances in the temperature of the refrigerant circulated by the refrigerant circulation device 30 can be suppressed. In other words, even if the liquid refrigerant or gas accepted into the buffer container 33 is at a relatively high temperature, since it can be mixed with the liquid refrigerant already stored in the buffer container 33 before flowing out of the buffer container 33, unwanted disturbances in the temperature of the refrigerant flowing downstream of the buffer container 33 can be suppressed.

[0066] The three-way valve 34 is located downstream of the portion of the refrigerant flow path 31 to which the heat exchanger 40, described later, is connected. The three-way valve 34 includes a first port 341, a second port 342, and a third port 343. The three-way valve 34 can adjust the flow rate of refrigerant flowing into the first port 341 and out through the second port 342, and the flow rate of refrigerant flowing into the first port 341 and out through the third port 343.

[0067] The three-way valve 34 forms part of the refrigerant flow path 31 in the passage between the first port 341 and the second port 342. The third port 343 is connected by a bypass passage 38 to the portion of the refrigerant flow path 31 upstream of the portion to which the heat exchanger 40 is connected. Specifically, the bypass passage 38 is connected to the buffer container 33. As a result, in this embodiment, the three-way valve 34 can send some or all of the refrigerant cooled by the heat exchanger 40 in the refrigerant flow path 31 to the buffer container 33 without sending it to the sealed container 10.

[0068] The amount of liquid refrigerant stored in the sealed container 10 can be increased or decreased depending on the operating state of the cooling system S1. If the amount of liquid refrigerant stored in the sealed container 10 becomes excessive, the risk of the pressure reducing device 20 drawing in the liquid refrigerant increases. For example, in such a case, the three-way valve 34 can prevent the amount of liquid refrigerant in the sealed container 10 from becoming excessive by reducing or blocking the flow rate of refrigerant to the sealed container 10.

[0069] In this embodiment, the three-way valve 34 is a proportional three-way valve. The three-way valve 34 may also be a valve whose valve body opening degree is adjusted by an electric motor such as a stepping motor or a servo motor, in which case the electric motor is electrically connected to the controller 100. However, the three-way valve 34 may also be an electromagnetically proportional three-way valve or a two-position three-way valve.

[0070] Furthermore, as described above, the second outlet 12 in the sealed container 10 is an opening for discharging the liquid refrigerant inside the sealed container 10. In this embodiment, the second outlet 12 is connected to the refrigerant flow path 31, more specifically to the buffer container 33, by a vent flow path 28. A vent control valve 29 is provided in the vent flow path 28. By opening the vent control valve 29, the liquid refrigerant inside the sealed container 10 can be directly discharged into the buffer container 33. The vent control valve 29 may also be opened if the amount of liquid refrigerant stored in the sealed container 10 becomes excessively large.

[0071] The heat exchanger 40 is connected to the downstream side of the circulation pump 32 and the upstream side of the three-way valve 34 in the refrigerant flow path 31. As described above, the cooling system S1 cools the heat medium circulated by the heat medium circulator 50 within the sealed container 10. The refrigerant circulation device 30 then releases the heat absorbed by the refrigerant from the heat medium through the heat exchanger 40. In other words, the heat exchanger 40 cools the liquid refrigerant circulating through the refrigerant flow path 31.

[0072] In this embodiment, the heat exchanger 40 is a liquid-cooled heat exchanger and is connected to a cooling water passage 44 through which cooling water for cooling the refrigerant flows. The cooling water may be water or another liquid. The heat exchanger 40 may also be an air-cooled heat exchanger.

[0073] The heat transfer medium circulating device 50 includes a heat transfer medium passage 51 through which the heat transfer medium is circulated, and a heat exchange unit 52 and a pump 53 provided in the heat transfer medium passage 51. In the heat transfer medium circulating device 50 in this embodiment, the heat exchange unit 52 and the pump 53 are provided between the upstream end 51A and the downstream end 51B of the heat transfer medium passage 51, and the upstream end 51A and the downstream end 51B of the heat transfer medium passage 51 are connected to the temperature-controlled object T. As a result, the heat transfer medium circulating device 50 circulates the heat transfer medium through the temperature-controlled object T.

[0074] More specifically, in this embodiment, the heat transfer medium channel 51 enters the sealed container 10 from the heat transfer medium inlet 15 and then extends outside the sealed container 10 from the heat transfer medium outlet 16. The upstream end 51A, the downstream end 51B, and the temperature-controlled object T of the heat transfer medium channel 51 are located outside the sealed container 10. Furthermore, in the heat transfer medium flow device 50 according to this embodiment, the heat exchange unit 52 is provided in the portion of the heat transfer medium channel 51 that is located inside the sealed container 10, that is, the heat exchange unit 52 is located inside the sealed container 10. As a result, the heat transfer medium channel 51 sends the heat transfer medium from outside the sealed container 10 to the heat exchange unit 52 and sends the heat-exchanged heat transfer medium from the heat exchange unit 52 to the outside of the sealed container 10.

[0075] The heat transfer medium is not particularly limited, but in this embodiment it is antifreeze. The heat transfer medium may be the same as the refrigerant circulated between the sealed container 10 and the heat exchanger 40. That is, the heat transfer medium is a substance that, for example, becomes -5°C or lower when expanded under atmospheric pressure and a standard ambient temperature (e.g., 25°C) in an environment of, for example, 0.1 atmospheres, and preferably a substance that becomes -30°C or lower when expanded in an environment of 0.01 atmospheres. If the refrigerant and the heat transfer medium are the same, it is advantageous in terms of manufacturing efficiency and cost. However, the heat transfer medium may be water or the like.

[0076] The heat exchange section 52 exchanges heat between the heat transfer medium being passed through and the refrigerant inside the sealed container 10. The heat exchange section 52 may be composed of a heat exchanger such as a finned tube, or it may be composed of tubular material and form a shell-and-tube configuration together with the sealed container 10. Alternatively, the heat exchange section 52 may be a structure that is in contact with the outer surface of the sealed container 10. In this case, the entire heat transfer medium passage device 50 will be located outside the sealed container 10.

[0077] The pump 53 is located outside the sealed container 10 in the heat transfer medium passage 51. The type of pump 53 is not particularly limited and may be a non-positive displacement pump or a positive displacement pump. The pump 53 includes a motor 53M controlled by an inverter, such as an AC motor or a brushless DC motor. The pump 53 can adjust the amount of liquid drawn in and thus the flow rate of the refrigerant flowing through the heat transfer medium passage 51 by adjusting the rotational speed of the motor 53M. The rotational speed of the motor 53M is adjusted by adjusting the frequency of the AC current supplied to the motor 53M using an inverter (not shown).

[0078] In this embodiment, the upstream end 51A and the downstream end 51B of the heat transfer medium flow path 51 are connected to the temperature-controlled object T. However, the heat transfer medium flow device 50 may also have a temperature control unit that connects the upstream end 51A and the downstream end 51B of the heat transfer medium flow path 51, and may be configured to exchange heat between the temperature control unit and the temperature-controlled object T. Alternatively, the heat transfer medium flow device 50 may be configured to discharge the heat transfer medium from the downstream end 50B.

[0079] The gas supply device 60 is connected to the gas inlet 14 of the sealed container 10 and is capable of supplying gas into the sealed container 10. The gas supply device 60 is provided, for example, to suppress a sudden drop in pressure inside the sealed container 10. Specifically, the gas supply device 60 can adjust the amount of gas supplied into the sealed container 10 according to the temperature inside the sealed container 10, the pressure inside the sealed container 10, the temperature of the heat transfer medium cooled by the refrigerant, or the temperature of the temperature-controlled object T.

[0080] The gas supply device 60, in more detail, includes a gas flow path 61, a gas flow control valve 62 provided in the gas flow path 61, and a gas source 63 connected to the upstream end of the gas flow path 61 and supplying gas to the gas flow path 61. The gas flow control valve 62 is electrically connected to the controller 100 and controlled by the controller 100. The gas flow control valve 62 may be a valve whose valve opening degree is adjusted by an electric motor such as a stepping motor or a servo motor. In this case, the controller 100 is electrically connected to the electric motor. The gas flow control valve 62 may also be an electromagnetic proportional valve or the like.

[0081] In this embodiment, the gas stored by the gas source 63 is nitrogen. However, the gas stored by the gas source 63 may be an inert gas such as neon or argon. It is desirable that the supplied gas is controlled to a temperature similar to that of the refrigerant inside the sealed container 10 when it is supplied into the sealed container 10.

[0082] Furthermore, the cooling system S1 includes a refrigerant temperature sensor 71 for detecting the temperature inside the sealed container 10, a pressure sensor 72 for detecting the pressure inside the sealed container 10, a liquid level sensor 73 for detecting the liquid level of the liquid refrigerant inside the sealed container 10, and a heat transfer medium temperature sensor 74 for detecting the temperature of the heat transfer medium that has been cooled by the refrigerant inside the sealed container 10 and flowed out to the outside of the sealed container 10.

[0083] The refrigerant temperature sensor 71 detects the temperature of the liquid refrigerant inside the sealed container 10 and identifies the detected temperature as the temperature inside the sealed container 10. However, the refrigerant temperature sensor 71 may also detect the temperature of the gas phase portion in the sealed container 10 and identify this as the temperature of the refrigerant inside the sealed container 10.

[0084] The pressure sensor 72 detects the pressure of the gas phase portion Gf inside the sealed container 10 and identifies the detected pressure as the pressure inside the sealed container 10. The liquid level sensor 73 is an optical sensor such as a laser displacement meter, which irradiates light onto the liquid surface of the refrigerant from the upper wall of the sealed container 10 and receives the reflected light to calculate the liquid level. However, the liquid level sensor 73 may be a float type sensor. The heat transfer medium temperature sensor 74 detects the temperature of the heat transfer medium flowing outside the sealed container 10, downstream of the heat exchange section 52 in the heat transfer medium flow path 51. Each sensor (71-74) is electrically connected to the controller 100, and the detection results of each sensor are sent to the controller 100.

[0085] The controller 100 is electrically connected to each of the sensors (71-74) described above, as well as to the gas suction pump 22, flow control valve 24, circulation pump 32, three-way valve 34, and gas flow control valve 62. The controller 100 may be composed of a computer having a CPU, ROM, etc. In this case, it performs various processes according to a program stored in the ROM. The controller 100 may also be composed of other processors or electrical circuits (for example, FPGA (Field Programmable Gate Alley)).

[0086] (Controller Functional Configuration) Figure 2 is a block diagram showing the functional configuration of the controller 100. As shown in Figure 2, the controller 100 includes a sensor information acquisition unit 101, a circulation pump adjustment unit 102, a bypass amount adjustment unit 103, a rotation speed adjustment unit 104, a valve opening adjustment unit 105, and a gas supply amount adjustment unit 106. The controller 100 may be composed of one computer or multiple computers. If it is composed of multiple computers, the above-mentioned functional units may be distributed among the multiple computers.

[0087] The sensor information acquisition unit 101 is the part that acquires detection results from the refrigerant temperature sensor 71, pressure sensor 72, liquid level sensor 73, and heat transfer medium temperature sensor 74, as described above. The sensor information acquisition unit 101 provides one or more pieces of information regarding the acquired detection results to the bypass amount adjustment unit 103, rotation speed adjustment unit 104, valve opening adjustment unit 105, and gas supply amount adjustment unit 106.

[0088] The circulation pump control unit 102 is electrically connected to the circulation pump 32 and controls the operation of the circulation pump 32. More specifically, the circulation pump control unit 102 is connected to the motor 32M of the circulation pump 32 via an inverter. The circulation pump control unit 102 adjusts the flow rate of refrigerant flowing through the refrigerant passage 31 by adjusting the frequency of the alternating current supplied from the inverter to the motor 32M.

[0089] The circulation pump adjustment unit 102 receives and holds the target flow rate of the refrigerant, for example, through an input device (not shown), and adjusts the rotational speed of the motor 32M of the circulation pump 32 so that the flow rate of the refrigerant matches the target flow rate.

[0090] The bypass volume adjustment unit 103 is electrically connected to the three-way valve 34 and controls the operation of the three-way valve 34. Specifically, the bypass volume adjustment unit 103 receives and holds the target height of the liquid refrigerant level in the sealed container 10, for example, through an input device (not shown). The bypass volume adjustment unit 103 then controls the three-way valve 34 using the detection result from the liquid level sensor 73 so that the liquid level of the liquid refrigerant in the sealed container 10 is maintained at the target height. In other words, the three-way valve 34 is controlled according to the difference between the liquid level detected by the liquid level sensor 73 and the target height.

[0091] Specifically, in this embodiment, in response to a command from the bypass amount adjustment unit 103, the three-way valve 34 reduces the flow rate of refrigerant flowing into the first port 341 and out of the second port 342, and increases the flow rate of refrigerant flowing into the first port 341 and out of the third port 343, when the liquid level of the liquid refrigerant in the sealed container 10 exceeds a predetermined height. Furthermore, the three-way valve 34 increases the flow rate of refrigerant flowing into the first port 341 and out of the second port 342, and decreases the flow rate of the refrigerant flowing into the first port 341 and out of the third port 343, when the liquid level of the liquid refrigerant in the sealed container 10 falls below a predetermined height.

[0092] Furthermore, the three-way valve 34 may, when the liquid level of the liquid refrigerant in the sealed container 10 exceeds a predetermined height, block the flow of refrigerant flowing into the first port 341 and out of the second port 342, while allowing the flow of refrigerant flowing into the first port 341 and out of the third port 343. On the other hand, the three-way valve 34 may, when the liquid level of the liquid refrigerant in the sealed container 10 falls below a predetermined height, allow the flow of refrigerant flowing into the first port 341 and out of the second port 342, while blocking the flow of refrigerant flowing into the first port 341 and out of the third port 343.

[0093] The rotation speed adjustment unit 104 is electrically connected to the gas suction pump 22 and controls the operation of the gas suction pump 22. More specifically, the rotation speed adjustment unit 104 is connected to the motor 22M of the gas suction pump 22 via an inverter. The rotation speed adjustment unit 104 adjusts the flow rate of gas passing through the gas passage 21 in the pressure reducing device 20 by adjusting the frequency of the alternating current supplied from the inverter to the motor 22M.

[0094] The rotation speed adjustment unit 104 receives and holds the target temperature of the heat transfer medium circulated by the heat transfer medium flow device 50, for example, via an input device (not shown). The rotation speed adjustment unit 104 adjusts the rotation speed of the motor 22M of the gas suction pump 22 so that the temperature detected by the heat transfer medium temperature sensor 74 matches the target temperature, thereby reducing the pressure inside the sealed container 10. In other words, the gas suction pump 22 may be controlled according to the difference between the temperature of the heat transfer medium, which is the result of detection from the heat transfer medium temperature sensor 74, and the target temperature.

[0095] In the control example described above, the gas suction pump 22 of the depressurization device 20 is controlled so that the temperature of the heat transfer medium matches the target temperature. However, instead, the rotational speed of the motor 22M may be adjusted so that the temperature inside the sealed container 10 (detection result of the refrigerant temperature sensor 71), the temperature of the temperature-controlled object T (detection result of a temperature sensor not shown), or the pressure inside the sealed container 10 matches the respective target values.

[0096] Furthermore, the valve opening adjustment unit 105 is electrically connected to the flow control valve 24 and controls the operation of the flow control valve 24. The valve opening adjustment unit 105 adjusts the flow rate of gas flowing through the gas passage 21 in the pressure reducing device 20 by adjusting the opening degree of the flow control valve 24.

[0097] The valve opening adjustment unit 105 may adjust the opening of the flow control valve 24 according to the temperature inside the sealed container 10 (detection result of the refrigerant temperature sensor 71), the pressure inside the sealed container 10 (detection result of the pressure sensor 72), the temperature of the heat transfer medium cooled by the refrigerant (detection result of the heat transfer medium temperature sensor 74), or the temperature of the temperature-controlled object T (detection result of a temperature sensor not shown). In this embodiment, such control of the flow control valve 24 may be performed after the gas suction pump 22 has been controlled so that the temperature of the heat transfer medium matches the target temperature, and the operating state of the gas suction pump 22 has been maintained constant. When the cooling operation actually starts, the temperature or pressure of the refrigerant inside the sealed container 10 may fluctuate. In such cases, the opening of the flow control valve 24 may be adjusted according to the temperature inside the sealed container 10, the pressure inside the sealed container 10, the temperature of the heat transfer medium cooled by the refrigerant, or the temperature of the temperature-controlled object T, so as to match the target temperature or target pressure.

[0098] The gas suction pump 22 and the flow control valve 24 may operate simultaneously. Alternatively, the operating state of the gas suction pump 22 may be kept constant and the opening degree of the flow control valve 24 may be adjusted, or the opening degree of the flow control valve 24 may be kept constant and the operating state of the gas suction pump 22 may be controlled.

[0099] Furthermore, the gas supply volume adjustment unit 106 is electrically connected to the gas flow control valve 62 and controls the operation of the gas flow control valve 62. The gas supply volume adjustment unit 106 adjusts the amount of gas supplied into the sealed container 10 by adjusting the opening degree of the gas flow control valve 62.

[0100] The gas supply device 60 may adjust the amount of gas supplied into the sealed container 10 according to the temperature inside the sealed container 10 (detection result of refrigerant temperature sensor 71), the pressure inside the sealed container 10 (detection result of pressure sensor 72), the temperature of the heat transfer medium cooled by the refrigerant (detection result of heat transfer medium temperature sensor 74), or the temperature of the temperature-controlled object T (detection result of temperature sensor not shown).

[0101] (Composition of refrigerant) Next, the refrigerant circulated in the cooling system S1 will be described. As mentioned above, in this embodiment, the refrigerant is, for example, a substance that is liquid at atmospheric pressure and a standard ambient temperature (e.g., 25°C), and when expanded from this state in an environment of, for example, 0.1 atmospheres, its temperature drops to -5°C or below, and preferably a substance that drops to -30°C or below when expanded in an environment of 0.01 atmospheres. Furthermore, it is desirable that the refrigerant be a low-environmental-impact refrigerant with a global warming potential (GWP) of 10 or less.

[0102] Specifically in this embodiment, HFO-1336mzz-Z, which has a GWP of 2 and is non-flammable, can be suitably used as the refrigerant. In this case, the heat transfer medium circulated by the heat transfer medium flow device 50 may also be HFO-1336mzz-Z. More specifically, the refrigerant may also be OpteonSF33(TM) manufactured by Mitsui Chemours Fluoroproducts Co., Ltd.

[0103] Figure 3 is the pH diagram for HFO-1336mzz-Z. HFO-1336mzz-Z starts at approximately 33°C, close to room temperature, at a pressure of about 0.100 MPa (near atmospheric pressure) (St1). When the pressure is reduced to 0.0149 MPa, the temperature drops to about -10°C (St2). Further reduction to 0.001 MPa lowers the temperature to below about -50°C. From state St2, where the temperature has dropped to about -10°C, it absorbs heat to some extent and evaporates (St3). From state St3, when it expands to approximately 0.100 MPa (near atmospheric pressure), the temperature rises to about 50°C, higher than room temperature, while remaining in the gas phase (St4). Finally, when cooled to room temperature from state St4, it condenses into a gas-liquid mixed phase and cools to about 33°C.

[0104] Such HFO-1336mzz-Z is cooled in the heat exchanger 40 and transitions to state St1 described above, and then flows into the sealed container 10, where it is depressurized and can transition to state St2, for example. Then, by exchanging heat with the heat transfer medium, HFO-1336mzz-Z can transition from state St2 to state St3, and then flows out of the sealed container 10 to the outside of the depressurization device 20, where it can transition from state St3 to state St4. Therefore, HFO-1336mzz-Z can be suitably used in the cooling system S1.

[0105] There are various other refrigerants that can be used in the cooling system S1, such as water or ethanol.

[0106] (operation) The following describes an example of the operation of the cooling system S1.

[0107] First, in the cooling system S1, the target temperature of the heat transfer medium circulated by the heat transfer medium flow device 50 is input and maintained. Then, after a predetermined amount of liquid refrigerant is filled into the sealed container 10, the reservoir tank 23, and the buffer container 33, the circulation pump 32 of the refrigerant circulation device 30 and the pump 53 of the heat transfer medium flow device 50 are driven. At this time, the three-way valve 34 and the vent control valve 29 are controlled so that the liquid level of the liquid refrigerant in the sealed container 10 reaches a predetermined height. After the liquid level of the liquid refrigerant in the sealed container 10 reaches the predetermined height, the three-way valve 34 blocks the flow of refrigerant flowing into the first port 341 and out through the second port 342, and allows the flow of refrigerant flowing into the first port 341 and out through the third port 343. In other words, a state is created in which liquid refrigerant does not flow from the refrigerant circulation device 30 into the sealed container 10.

[0108] Subsequently, the depressurization device 20 is activated, and the pressure inside the sealed container 10 is reduced to a pressure lower than atmospheric pressure by the depressurization device 20. The depressurization device 20 adjusts the rotation speed of the motor 22M of the gas suction pump 22 until the temperature detected by the heat transfer medium temperature sensor 74 matches the target temperature. After the temperature detected by the heat transfer medium temperature sensor 74 matches the target temperature, at least one of the following is controlled to maintain the target temperature: the rotation speed of the motor 22M of the gas suction pump 22, the opening degree of the flow control valve 24, and the opening degree of the gas flow control valve 62 of the gas supply device 60. With this, the startup operation is completed. After the rotation speed of the motor 22M of the gas suction pump 22 has been adjusted so that the temperature detected by the heat transfer medium temperature sensor 74 matches the target temperature, the pressure inside the sealed container 10 is reduced to a pressure lower than atmospheric pressure by the pressure reducing device 20, and the refrigerant flow environment in the refrigerant circulation device 30 and the refrigerant flow environment in the heat exchanger 40, which are outside the sealed container 10, are set to a pressure higher than the pressure inside the sealed container 10, for example, to atmospheric pressure. However, the refrigerant flow environment in the refrigerant circulation device 30 and the refrigerant flow environment in the heat exchanger 40 do not have to be exactly atmospheric pressure, and may be slightly lower than atmospheric pressure.

[0109] Subsequently, the heat transfer medium circulating through the heat transfer medium circulator 50 transitions to a state where it cools the temperature-controlled object T. The refrigerant flows out of the sealed container 10, is cooled in the cooling unit 25 and the heat exchanger 40, and then flows back into the sealed container 10. As a result, the heat transfer medium is continuously cooled by the refrigerant.

[0110] In other words, using Figure 3 to explain the operating state of the cooling system S1, the refrigerant that has absorbed heat from the heat transfer medium flows out of the sealed container 10 and is cooled in the cooling unit 25 and heat exchanger 40, transitioning from state St4 to state St1 in Figure 3. Subsequently, the refrigerant is depressurized by flowing back into the sealed container 10 and transitions to state St2. Then, the refrigerant exchanges heat with the heat transfer medium in the sealed container 10, transitioning from state St2 to state St3. Subsequently, the refrigerant flows out of the sealed container 10 to the depressurization device 20, transitioning from state St3 to state St4. Then, the refrigerant is cooled in the cooling unit 25 and heat exchanger 40, transitioning from state St4 to state St1. As a result, the heat transfer medium is continuously cooled by the refrigerant.

[0111] The cooling system S1 according to the first embodiment described above includes a sealed container 10 for storing liquid refrigerant, which includes a first outlet 11 and an inlet 13; a pressure reducing device 20 connected to the first outlet 11 that adjusts the pressure inside the sealed container 10 to a pressure lower than atmospheric pressure by sucking gas from the sealed container 10 through the first outlet 11; and a refrigerant circulation device 30 which includes a refrigerant flow path 31 connected to the pressure reducing device 20 and the inlet 13, and causes the liquid refrigerant, which has liquefied from the gas sucked from the sealed container 10 by the pressure reducing device 20, to flow into the sealed container 10 through the inlet 13. The cooling system S1 according to the first embodiment described above includes a sealed container 10 for storing liquid refrigerant, which includes a first outlet 11 and an inlet 13 for storing liquid refrigerant; a pressure reducing device 20 that adjusts the pressure inside the sealed container 10 to a pressure lower than atmospheric pressure; and a refrigerant circulation device 30 connected to the pressure reducing device 20 and the inlet 13, which causes the liquid refrigerant to flow into the sealed container 10 through the inlet 13. The temperature-controlled object T is cooled by the refrigerant inside the sealed container 10.

[0112] Such a cooling system S1 makes it possible to use substances that were not used in conventional refrigeration methods as refrigerants in the thermal cycle, or expands the range of substances that can be used as refrigerants in the thermal cycle.

[0113] In other words, as described above, in this embodiment, as an example, a substance that is liquid at atmospheric pressure and a standard ambient temperature (e.g., 25°C) and that, when expanded in an environment of, for example, 0.1 atmospheres, becomes -5°C or lower can be used as a refrigerant. In contrast, if the above substance is used in a conventional vapor compression type refrigeration cycle, for example, the compressor will compress the liquid, causing the compressor to malfunction and preventing the substance from evaporating in the evaporator. Therefore, the above refrigerant is not suitable for a vapor compression type refrigeration cycle. In contrast, the cooling system S1 does not utilize compression and can cool the heat transfer medium by reducing the pressure of the above refrigerant in the sealed container 10, allowing the heat from the heat transfer medium to be released from the cooling unit 25 and the heat exchanger 40, thereby realizing a thermal cycle. Therefore, according to this embodiment, substances that were not used in conventional refrigeration methods can be used as refrigerants in the thermal cycle, or the range of substances that can be used as refrigerants in the thermal cycle can be expanded. In this embodiment, the depressurization device 20 is equipped with a cooling unit 25, and heat is dissipated between the cooling unit 25 and the heat exchanger 40. On the other hand, a configuration in which heat is dissipated only by the cooling unit 25 without a heat exchanger 40 may be adopted, or heat may be dissipated only by the heat exchanger 40 without a cooling unit 25.

[0114] Furthermore, as mentioned above, the cooling system S1 allows the use of a refrigerant such as HFO-1336mzz-Z, which has a GWP of 2 and is non-flammable. This enables low GWP and safe cooling operation, which is not currently achievable with vapor compression refrigeration cycles. Such a low GWP, environmentally friendly, and safe cooling system S1 is unknown, including other cooling methods. Therefore, the realization of such a cooling system S1 has the potential to make a significant contribution to protecting the global environment. In addition, since the cooling system S1 does not use a compressor, the leakage of lubricating oil into the refrigerant side is suppressed, which is also beneficial.

[0115] Furthermore, this embodiment incorporates various features to enable economical and stable operation of the cooling system S1.

[0116] For example, the pressure reducing device 20 includes a gas flow path 21 connected to the first outlet 11, a gas suction pump 22 provided in the gas flow path 21 for drawing gas from the sealed container 10 into the gas flow path 21, and a reservoir tank 23 connected to the downstream end 21B of the gas flow path 21 for storing the gas flowing out from the downstream end 21B. This makes it easier to vaporize the gas in the reservoir tank 23, and suppresses the situation in which the refrigerant in gaseous state returns to the sealed container 10 by the refrigerant circulation device 30.

[0117] In particular, in this embodiment, the pressure in the reservoir tank 23 is higher than the pressure in the sealed container 10, and the reservoir tank 23 liquefies at least a portion of the gas flowing out from the downstream end 21B of the gas flow path 21 into liquid refrigerant and stores the liquid refrigerant. This effectively suppresses the situation in which gaseous refrigerant returns to the sealed container 10 by the refrigerant circulation device 30.

[0118] Furthermore, the refrigerant circulation device 30 further includes a buffer container 33 provided in the refrigerant flow path 31 so as to form a part of the refrigerant flow path 31, and which stores liquid refrigerant. The gas or liquid refrigerant, in which at least a portion of the gas has been liquefied, stored in the reservoir tank 23 is then introduced into the buffer container 33. In this configuration, the gas or liquid refrigerant from the reservoir tank 23 can be mixed with the liquid refrigerant stored in the buffer container 33 before flowing out of the buffer container 33. This helps to suppress undesirable disturbances in the temperature of the refrigerant flowing downstream of the buffer container 33.

[0119] Furthermore, the refrigerant circulation device 30 is provided in the portion of the refrigerant flow path 31 downstream of the portion to which the heat exchanger 40 is connected, and includes a three-way valve 34 with a first port 341, a second port 342, and a third port 343. The three-way valve 34 constitutes a part of the refrigerant flow path 31 in the flow path between the first port 341 and the second port 342. The third port 343 and the portion of the refrigerant flow path 31 upstream of the portion to which the heat exchanger 40 is connected (the buffer container 33 in this embodiment) are connected by a bypass flow path 38.

[0120] This enables stable operation of the cooling system S1 and improves the accuracy of temperature control. For example, if the amount of liquid refrigerant stored in the sealed container 10 becomes excessive, the risk of the pressure reducing device 20 drawing in the liquid refrigerant increases. In this case, there is a risk that the operation of the pressure reducing device 20 will become unstable or that the pressure reducing device 20 will be damaged. For example, in such a case, the three-way valve 34 can prevent a situation in which there is an excessive amount of liquid refrigerant in the sealed container 10 by reducing or blocking the flow rate of refrigerant passing to the sealed container 10.

[0121] <Second Embodiment> Next, the cooling system S2 according to the second embodiment will be described with reference to Figure 4. Components in this embodiment that are the same as those in the first embodiment are denoted by the same reference numerals, and redundant descriptions are omitted.

[0122] This embodiment differs from the first embodiment in that it does not have a vent passage 28 connecting the sealed container 10 and the buffer container 33, nor a vent control valve 29 on the vent passage 28. The cooling system S2 according to this second embodiment also provides the same effects as the first embodiment. Furthermore, this embodiment simplifies the device configuration.

[0123] <Third Embodiment> Next, the cooling system S3 according to the third embodiment will be described with reference to Figure 5. Components in this embodiment that are the same as those in the first and second embodiments are denoted by the same reference numerals, and redundant descriptions are omitted.

[0124] In this embodiment, the refrigerant circulation device 30 does not include a circulation pump 32 and a three-way valve 34. A heat exchanger 40 is arranged inside the buffer container 33. The heat exchanger 40 may be configured to be in contact with the outer wall of the buffer container 33, or it may be connected to the upstream or downstream portion of the buffer container 33 in the refrigerant flow path 31.

[0125] In this embodiment, a return volume adjustment valve 80 is provided in the refrigerant flow path 31. The return volume adjustment valve 80 is a valve that adjusts the flow rate of liquid refrigerant flowing from the reservoir tank 23 into the sealed container 10. Specifically, the return volume adjustment valve 80 is controlled by the controller 100 and adjusts the flow rate of liquid refrigerant flowing into the sealed container 10 so that, for example, the liquid level of the liquid refrigerant in the sealed container 10 is maintained at a predetermined height. The return volume adjustment valve 80 may be an on-off valve or a proportional valve.

[0126] The following describes an example of the operation of the cooling system S3.

[0127] First, in the cooling system S3, the target temperature of the heat transfer medium circulated by the heat transfer medium flow device 50 is input and maintained. Then, after a predetermined amount of liquid refrigerant is filled into the sealed container 10, the reservoir tank 23, and the buffer container 33, the pump 53 of the heat transfer medium flow device 50 is driven. At this time, the return amount control valve 80 is controlled so that the liquid level of the liquid refrigerant in the sealed container 10 reaches a predetermined height. In this embodiment, when the return amount control valve 80 is opened, the liquid refrigerant flows naturally into the sealed container 10 by its own gravity, but a circulation pump 32 may also be provided. After the liquid level of the liquid refrigerant in the sealed container 10 reaches the predetermined height, the return amount control valve 80 is closed.

[0128] Subsequently, the pressure reducing device 20 is activated, and the pressure inside the sealed container 10 is reduced to a pressure lower than atmospheric pressure by the pressure reducing device 20. The pressure reducing device 20 adjusts the rotation speed of the motor 22M of the gas suction pump 22 until the temperature detected by the heat transfer medium temperature sensor 74 matches the target temperature. After the temperature detected by the heat transfer medium temperature sensor 74 matches the target temperature, at least one of the rotation speed of the motor 22M of the gas suction pump 22, the opening degree of the flow control valve 24, and the opening degree of the gas flow control valve 62 of the gas supply device 60 is controlled to maintain the target temperature. With this, the startup operation is completed. In the state after the rotation speed of the motor 22M of the gas suction pump 22 has been adjusted so that the temperature detected by the heat transfer medium temperature sensor 74 matches the target temperature, the pressure inside the sealed container 10 is reduced to a pressure lower than atmospheric pressure by the pressure reducing device 20, and the refrigerant flow environment in the refrigerant circulation device 30 outside the sealed container 10 is set to a pressure higher than the pressure inside the sealed container 10, for example, to atmospheric pressure. However, the refrigerant flow environment in the refrigerant circulation device 30 does not have to be strictly atmospheric pressure; it may be at a pressure slightly lower than atmospheric pressure.

[0129] Subsequently, the heat transfer medium circulating through the heat transfer medium circulator 50 transitions to a state where it cools the temperature-controlled object T. The refrigerant flows out of the sealed container 10, is cooled in the cooling unit 25 and the heat exchanger 40, and then flows back into the sealed container 10. As a result, the heat transfer medium is continuously cooled by the refrigerant.

[0130] The cooling system S3 according to this third embodiment also provides the same effects as the first embodiment, while simplifying the device configuration.

[0131] <Fourth Embodiment> Next, the cooling system S4 according to the fourth embodiment will be described with reference to Figure 6. Components in this embodiment that are the same as those in the first to third embodiments are denoted by the same reference numerals, and redundant descriptions are omitted.

[0132] This embodiment further simplifies the system by removing the buffer container 33 from the refrigerant circulation device 30 in the third embodiment and also by not using the heat exchanger 40. The cooling system S4 can be operated in the manner described in the third embodiment. Such an embodiment is beneficial in terms of simplifying the device.

[0133] Although various embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various further modifications can be made to the above embodiments.

Claims

1. A container for storing liquid refrigerant, including an outlet and an inlet, A pressure reducing device connected to the outlet, which adjusts the pressure inside the container to a pressure lower than atmospheric pressure by drawing gas from the container through the outlet, A refrigerant circulation device is provided, which includes a refrigerant flow path connected to the pressure reducing device and the inlet, and which causes the liquid refrigerant liquefied from the gas drawn from the container by the pressure reducing device to flow into the container through the inlet, The cooling system includes a refrigerant flow path that includes a valve for adjusting the flow rate of the liquid refrigerant flowing into the container.

2. The cooling system according to claim 1, wherein, in a state where the liquid refrigerant does not flow into the container due to the valve, the depressurizing device adjusts the pressure inside the container to a pressure less than atmospheric pressure.

3. The cooling system according to claim 1 or 2, wherein the valve is opened and closed so that the liquid level of the liquid refrigerant in the container is maintained at a predetermined height.

4. The cooling system according to claim 1, wherein the temperature of the object to be temperature controlled is controlled by the refrigerant in the container.

5. A cooling method comprising a cooling system comprising: a container for storing liquid refrigerant, including an outlet and an inlet; a depressurizing device connected to the outlet for drawing gas from the container through the outlet; and a refrigerant circulation device, including a refrigerant flow path connected to the depressurizing device and the inlet, for flowing the liquid refrigerant, liquefied from the gas drawn from the container by the depressurizing device, into the container through the inlet, wherein the cooling system comprises: A startup operation is performed to adjust the pressure inside the container to a pressure lower than atmospheric pressure. A cooling method comprising: after the completion of the startup operation, the refrigerant circulation device introducing the liquid refrigerant into the container and controlling the temperature of the temperature-controlled object.

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