WO2024085167A1

WO2024085167A1 - Cooling system

Info

Publication number: WO2024085167A1
Application number: PCT/JP2023/037634
Authority: WO
Inventors: 知行苅谷; 朝禎笹渕
Original assignee: 伸和コントロールズ株式会社
Priority date: 2022-10-18
Filing date: 2023-10-18
Publication date: 2024-04-25

Abstract

A cooling system according to an embodiment of the present invention comprises: a sealed container 10 that includes a first outflow port 11 and an inflow port 13, and that stores a liquid refrigerant; a pressure reduction device 20 that is connected to the first outflow port 11 and adjusts the pressure in the sealed container 10 to be lower than the atmospheric pressure by sucking a gas from the sealed container 10 through the first outflow port 11; and a refrigerant circulation device 30 that includes a refrigerant flow channel 31 connected to the pressure reduction device 20 and the inflow port 13 and that allows the liquid refrigerant, obtained by liquefying the gas sucked from the sealed container 10 by the pressure reduction device 20, to flow through the inflow port 13 into the sealed container 10.

Description

Cooling System

The embodiment of the present invention relates to a cooling system that utilizes a decrease in the temperature of a refrigerant caused by reduced pressure.

Vapor compression refrigeration systems are widely used in many fields.

In a vapor compression refrigeration system, the refrigerant is compressed in the compressor, and the refrigerant flowing out of the compressor is cooled in the condenser. The refrigerant flowing out of the condenser is expanded in the expansion valve, and the refrigerant flowing out of the expansion valve exchanges heat with the temperature-controlled object in the evaporator. The refrigerant cools the object by absorbing heat from the temperature-controlled object in the evaporator. The refrigerant flowing out of the evaporator circulates to the compressor, and then releases heat in the condenser.

The refrigerants used in vapor compression refrigeration units are usually fluorinated refrigerants. Fluorinated refrigerants are greenhouse gases and can be flammable, but they offer various advantages, such as the ability to achieve highly efficient operation.

On the other hand, in consideration of the impact that fluorine-based refrigerants have on the environment, development of fluorine-based refrigerants for vapor compression systems that can keep the global warming potential (GWP) low has been progressing. HFO-based refrigerants for vapor compression systems with very low GWP have already been put to practical use. Specifically, for example, HFO-based refrigerants with a GWP of 10 or less have been put to practical use. However, it cannot be said that these refrigerants are fully safe in terms of flammability and toxicity. For this reason, development of refrigerants for vapor compression systems that can ensure low GWP and safety is still being actively pursued.

In addition, the compressors used in vapor compression refrigeration systems operate for long periods of time. For this reason, it is necessary to lubricate the rotating parts and other moving parts with lubricating oil. However, there is a problem with lubricating oil leaking into the refrigerant side. This leakage of lubricating oil can cause the compressor to run out of oil, which can impair the stability of the compressor's operation. Furthermore, retention of lubricating oil in the evaporator can impair the cooling efficiency of the evaporator. For this reason, vapor compression refrigeration systems have room for various improvements in terms of the use of compressors.

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

When exchanging heat between the liquid and the temperature-controlled object, the boiling cooling device vaporizes the liquid, and can efficiently cool the temperature-controlled object by absorbing heat through latent heat. Normally, a pump is required to circulate the liquid or the gas that has been vaporized, but the pump does not require lubricating oil, or if it does, only a small amount is required. Furthermore, the energy consumption of the pump is relatively small. Therefore, the boiling cooling device can be said to be a device with excellent environmental performance.

However, in a boiling cooling device, the temperature of the circulating liquid is usually close to its boiling point under atmospheric pressure, and cooling at temperatures well below 0°C is not possible, for example, and the cooling temperature and temperature control targets are severely restricted. For this reason, it is difficult to ensure high refrigeration capacity at low or ultra-low temperature ranges using a boiling cooling device.

In recent years, while the development of HFO refrigerants has progressed as described above, the development of antifreeze with low environmental impact has also progressed. HFO solvents that have low GWP and are non-flammable and can be used as antifreeze have been put into practical use. Such solvents have boiling points of, for example, 70°C or higher under atmospheric pressure, and are therefore not suitable for vapor compression refrigeration equipment. However, if a thermal cycle can be realized using such HFO solvents, it may be possible to realize a cooling system that can ensure low environmental impact, high safety, and high refrigeration capacity, which are currently strongly desired.

The inventors therefore conducted intensive research to realize a new cooling system that can enable the use of HFO-based solvents such as those mentioned above as refrigerants in a thermal cycle. More generally, they conducted intensive research to realize a new cooling system that can shift a range of substances that is different from the range of refrigerants that can be used in vapor compression refrigeration devices to refrigerants that can be used in a thermal cycle. They discovered that the above cooling system could be realized by a structure in which the temperature of the refrigerant is lowered by reducing the pressure to cool it, and then the heat absorbed by the refrigerant is released under atmospheric pressure, which led to the invention of the present invention.

In other words, the object of the present invention is to provide a cooling system that allows substances that have not been used in conventional refrigeration methods to be used as refrigerants in a heat cycle, or that can expand the range of substances that can be used as refrigerants in a heat cycle.

One embodiment of the present invention relates to the following aspects "1" to "18".

[1] A container including an outlet and an inlet and configured to store a liquid refrigerant;
a pressure reducing device connected to the outlet and configured to adjust the pressure in the container to a pressure lower than atmospheric pressure by sucking gas from the container through the outlet;
a refrigerant circulation device including a refrigerant flow path connected to the pressure reducing device and the inlet, the refrigerant being liquefied from the gas sucked from the container by the pressure reducing device and flowing into the container through the inlet,
A cooling system that cools a temperature-controlled object using the refrigerant in the container.

[2] The pressure reducing device is
A gas flow path connected to the outlet;
a gas suction pump provided in the gas flow path and configured to suck the gas from the container into the gas flow path;
a reservoir tank connected to the gas flow path and configured to store the gas flowing out of the gas flow path and/or the refrigerant in a liquid state liquefied from the gas,
The cooling system according to claim 1, wherein the refrigerant flow path is connected to the reservoir tank.

[3] The cooling system described in [2], in which 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 flow path into the liquid refrigerant and stores the liquid refrigerant.

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

[5] The cooling system according to any one of [2] to [4], wherein the pressure reducing device further includes a cooling unit that cools a portion of the gas flow path downstream of the gas suction pump and/or the reservoir tank.

[6] The refrigerant circulating device further includes a buffer container that is provided in the refrigerant flow path so as to form a part of the refrigerant flow path and stores the refrigerant in a liquid state,
The cooling system according to any one of claims 2 to 5, wherein the liquid refrigerant drawn from the reservoir tank into the refrigerant flow path passes through the buffer container and then flows into the container.

[7] The cooling system further includes a heat exchanger connected to the refrigerant flow path and configured to cool the liquid refrigerant flowing through the refrigerant flow path,
The cooling system according to claim 6, wherein the buffer container is provided in a portion of the refrigerant flow path upstream of a portion to which the heat exchanger is connected.

[8] A cooling system as described in [6] or [7], in which the reservoir tank is disposed above the buffer container.

[9] The gas suction pump is configured to suck the gas by rotation of a motor,
The cooling system according to any one of [2] to [8], wherein the gas suction pump adjusts the rotation speed of the motor in accordance with the temperature in the container, the pressure in the container, the temperature of the heat medium cooled by the refrigerant, or the temperature of the temperature-controlled object.

[10] A flow control valve is provided in the gas flow path on the upstream or downstream side of the gas suction pump to control the flow rate of the gas flowing through the gas flow path by adjusting the opening degree,
The cooling system according to any one of [2] to [9], wherein the flow control valve adjusts its opening degree according to the temperature in the container, the pressure in the container, the temperature of the heat medium cooled by the refrigerant, or the temperature of the temperature-controlled object.

[11] Further comprising a gas supply device for supplying gas into the container,
The cooling system according to any one of [2] to [10], wherein the gas supply device adjusts the amount of the gas supplied into the container in accordance with the temperature in the container, the pressure in the container, the temperature of the heat medium cooled by the refrigerant, or the temperature of the temperature-controlled object.

[12] The cooling system further includes a heat exchanger connected to the refrigerant flow path and configured to cool the liquid refrigerant flowing through the refrigerant flow path,
the refrigerant circulation device is provided in a portion of the refrigerant flow path downstream of a portion 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 a flow rate of the refrigerant flowing into the first port and flowing out from the second port, and a 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 with a 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 a portion to which the heat exchanger is connected are connected by a bypass flow path.

[13] When a liquid level of the refrigerant in a liquid state in the container exceeds a predetermined level, the three-way valve reduces a flow rate of the refrigerant flowing into the first port and flowing out of the second port and increases a flow rate of the refrigerant flowing into the first port and flowing out of the third port,
The cooling system of [12], wherein the three-way valve increases a flow rate of the refrigerant flowing into the first port and flowing out of the second port and decreases a flow rate of the refrigerant flowing into the first port and flowing out of the third port when a liquid level of the refrigerant in the container falls below a predetermined level.

[14] When a liquid level of the refrigerant in a liquid state in the container exceeds a predetermined level, the three-way valve blocks the flow of the refrigerant flowing into the first port and flowing out of the second port and allows the flow of the refrigerant flowing into the first port and flowing out of the third port,
The cooling system of [12], wherein the three-way valve allows the refrigerant to flow into the first port and flow out of the second port and blocks the flow of the refrigerant to flow into the first port and flow out of the third port when a liquid level of the refrigerant in the container falls below a predetermined level.

[15] The heating device further includes a heat medium flow device including a heat medium flow path through which the heat medium flows,
the heat medium flow path includes a heat exchange portion disposed in the container and exchanging heat between the heat medium and the refrigerant;
The cooling system according to any one of [1] to [14], wherein the heat medium flow path sends the heat medium from outside the container to the heat exchange section and sends the heat medium that has been heat exchanged in the heat exchange section to the outside of the container.

[16] A cooling system according to any one of [1] to [15], in which the refrigerant is a substance whose boiling point at atmospheric pressure is 30°C or higher.

[17] A cooling system according to any one of [1] to [16], wherein the refrigerant has a GWP of 10 or less.

[18] A cooling system according to any one of [1] to [17], wherein the refrigerant is HFO-1336mzz-Z.

The present invention makes it possible to use substances that have not been used in conventional refrigeration methods as refrigerants in heat cycles, or to expand the range of substances that can be used as refrigerants in heat cycles.

1 is a diagram illustrating a cooling system according to a first embodiment. 2 is a block diagram showing a functional configuration of a controller constituting the cooling system of FIG. 1 . FIG. 2 is a ph diagram of an example of a refrigerant used in the cooling system of FIG. 1. FIG. 13 is a diagram illustrating a cooling system according to a second embodiment. FIG. 13 is a diagram illustrating a cooling system according to a third embodiment. FIG. 13 is a diagram illustrating a cooling system according to a fourth embodiment.

Each embodiment is explained below.

First Embodiment
1 is a schematic diagram of a cooling system S1 according to a first embodiment. First, the configuration of the cooling system S1 will be described.

(Cooling system configuration)
As shown in FIG. 1 , a cooling system S1 according to the first embodiment includes a sealed container 10, a pressure reducing device 20, a refrigerant circulating device 30, a heat exchanger 40, a heat medium circulating device 50, a gas supplying device 60, and a controller 100.

In the cooling system S1, a liquid refrigerant is stored in the sealed container 10. The pressure reducing device 20 is connected to the sealed container 10 and reduces the pressure in the sealed container 10 by sucking in the gas present in the sealed container 10 or the gas evaporated in the sealed container 10. The refrigerant circulation device 30 is connected to the pressure reducing device 20 and causes the liquid refrigerant liquefied from the gas sucked from the sealed container 10 by the pressure reducing device 20 to flow and flow back into the sealed container 10. The refrigerant circulation device 30 is also connected to the heat exchanger 40 outside the sealed container 10. As a result, the refrigerant circulated by the refrigerant circulation device 30 circulates between the sealed container 10 and the heat exchanger 40. The cooling system S1 cools the heat medium circulated by the heat medium circulating device 50 in the sealed container 10, and the heat medium circulating device 50 sends the cooled heat medium to the temperature control target T. The refrigerant circulation device 30 also releases the heat absorbed by the refrigerant from the heat medium from the heat exchanger 40. Furthermore, in this embodiment, the pressure reducing device 20 also releases heat from the cooling section 25 described below. This allows the heat medium to be continuously cooled.

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

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

The sealed container 10 includes a first outlet 11, a second outlet 12, an inlet 13, a gas receiving port 14, a heat medium inlet 15, and a heat medium outlet 16, and is a container that prevents the outflow and leakage of gas and liquid from any part other than these ports (11-16). The sealed container 10 is constructed in a structure that allows it to maintain its shape when the internal pressure is reduced, and is a so-called vacuum insulated container.

Whether the sealed container 10 maintains its shape when decompressed depends on the internal pressure to be reduced, but when the pressure is reduced to, for example, 0.1 atmospheres, it is preferable that the outer shell of the sealed container 10 is formed from a thick, hard metal or the like. However, the specific structure of the sealed container 10 can be appropriately determined according to the expected degree of pressure reduction, and is not particularly limited. The sealed container 10 may also include a container body with an opening, and a lid for opening and closing the opening. In this case, it is necessary to ensure sufficient airtightness and sealing when the lid is closed.

The sealed container 10 is configured to store liquid refrigerant, with the symbol Lf indicating a pool of liquid refrigerant and the symbol Gf indicating a gas phase portion. That is, in this embodiment, the sealed container 10 stores liquid refrigerant while forming a gas phase portion Gf. The pressure reducing device 20, which will be described later, reduces the pressure inside the sealed container 10 by sucking in the gas inside the sealed container 10. Here, when the gas phase portion Gf is formed, the 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, breakdowns in the pressure reducing device 20 can be suppressed.

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

The first outlet 11 is connected to the pressure reducing device 20 and is an opening intended to allow gas to flow out. Therefore, it is preferable that it opens in the gas phase portion Gf of the sealed container. In addition, the gas receiving port 14 is connected to the gas supply device 60 as described below, and this gas receiving port 14 also preferably opens in the gas phase portion Gf of the sealed container 10, similar to the first outlet 11. The first outlet 11 and the gas receiving port 14 are preferably provided in the upper part of the top wall or side wall of the sealed container 10. In the illustrated example, the first outlet 11 and the gas receiving port 14 are formed in the top wall of the sealed container 10.

The second outlet 12 is an opening for discharging the liquid refrigerant in the sealed container 10. The inlet 13 is an opening for receiving the liquid refrigerant circulated by the refrigerant circulation device 30. The second outlet 12 and the inlet 13 preferably open to the liquid phase portion of the sealed container 10, and are preferably provided in the bottom wall or the lower part of the 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 middle position in the vertical direction of the side wall of the sealed container 10. In addition, the heat medium inlet 15 and the heat medium outlet 16 preferably open to the liquid phase portion of the sealed container 10, and in the illustrated example, the heat medium inlet 15 and the heat medium outlet 16 are formed in the bottom wall of the sealed container 10.

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. In more detail, 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 and 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 and storing the gas flowing out from the downstream end 21B.

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 provided in a portion of the gas flow path 21 between the upstream end 21A and the downstream end 21B.

The type of the gas suction pump 22 is not particularly limited, but it is preferable that it is a dry vacuum pump in which lubricating oil does not flow out or hardly flows out into 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 is different from the types exemplified above. However, the gas suction pump 22 may also be a wet vacuum pump.

In this embodiment, the gas suction pump 22 is a dry vacuum pump. The gas suction pump 22 includes a motor 22M, such as an AC motor or a brushless DC motor, that is controlled by an inverter. The gas suction pump 22 can adjust the amount of gas suctioned and the pressure inside the sealed container 10 by adjusting the rotation speed of the motor 22M. More specifically, the rotation 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).

In addition, 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 of the flow control valve 24. The flow control valve 24 can adjust the flow rate of the gas flowing through the gas flow path 21 by adjusting its opening. This adjusts the amount of gas suction, making it possible to adjust the pressure inside the sealed container 10.

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

In this embodiment, the flow control valve 24 is provided in the gas flow path 21 upstream of the gas suction pump 22, but may be provided downstream of the gas suction pump 22. The flow control valve 24 is, for example, a butterfly valve, but is not limited to this.

The gas suction pump 22 and the flow control valve 24 are electrically connected to the controller 100 and are 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 that adjusts the opening of the valve body 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 be an electromagnetic proportional valve, etc.

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 makes it easier for 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 and store the liquid refrigerant. The reservoir tank 23 may have, for example, an openable lid to reduce power consumption of the gas suction pump 22 when the pressure rises, for safety reasons, and for filling or replenishing the refrigerant. That is, the reservoir tank 23 may have 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.

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

The refrigerant circulation device 30 includes a refrigerant flow path 31 that connects the pressure reducing device 20 and the inlet 13, and a circulation pump 32 that is provided in the refrigerant flow path 31 and draws liquid refrigerant in the reservoir tank 23 into the refrigerant flow path 31. More 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 causes it to flow into the sealed container 10 from the inlet 13.

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, the buffer container 33, and the three-way valve 34 are provided in the refrigerant flow path 31 so as to each form part of the refrigerant flow path 31. The circulation pump 32 is disposed downstream of the buffer container 33, and the three-way valve 34 is disposed downstream of the circulation pump 32, but such an arrangement is not particularly limited.

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, the buffer container 33, and the 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.

The type of the circulation pump 32 is not particularly limited, and it may be a non-positive-displacement pump or a positive-displacement pump. The circulation pump 32 includes a motor 32M, such as an AC motor or a brushless DC motor, that is controlled by an inverter. The circulation pump 32 adjusts the amount of liquid drawn in by adjusting the rotation speed of the motor 32M, and is capable of adjusting the flow rate of the refrigerant flowing through the refrigerant flow path 31. More specifically, the rotation 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).

In addition, when the refrigerant passes through the circulation pump 32, the pressure of the refrigerant is increased. When the pressure of the refrigerant is increased, the temperature of the refrigerant rises. The above-mentioned heat exchanger 40 is connected to the refrigerant flow path 31, and 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.

The buffer container 33 includes an inlet 33A that receives the refrigerant drawn from the reservoir tank 23, and an outlet 33B that allows the refrigerant to flow out. As a result, the liquid refrigerant drawn from the reservoir tank 23 into the refrigerant flow path 31 passes through the buffer container 33 from the inlet 33A through the outlet 33B, and then flows into the sealed container 10.

The buffer container 33 is adapted 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 have to be filled with liquid refrigerant. However, the greater 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 perspective, it is preferable that the storage space of the buffer container 33 is filled with liquid refrigerant, and even if this is not the case, the amount of liquid refrigerant stored in the storage space of the buffer container 33 is preferably 50% or more in terms of volume ratio to the storage space, and may be 70% or more, 80% or more, or 90% or more.

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

The buffer container 33 receives liquid refrigerant from the receiving port 33A, but in this embodiment, the reservoir tank 23 is disposed above the buffer container 33, so that the liquid refrigerant stored in the reservoir tank 23 can be smoothly sent to the buffer container 33 by its own weight. The receiving port 33A is provided at the top of the buffer container 33, specifically on the top wall, which makes it possible to reduce the piping length of the portion of the refrigerant flow path 31 between the reservoir tank 23 and the buffer container 33.

The buffer container 33 basically receives liquid refrigerant from the receiving port 33A, but may also receive gas containing unliquefied vaporized refrigerant. Here, the liquid refrigerant or gas received in the buffer container 33 may be relatively high in temperature, but when liquid refrigerant or gas from the reservoir tank 23 flows into the buffer container 33 that stores liquid refrigerant, undesired 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 received in the buffer container 33 is relatively high in temperature, the refrigerant or gas can flow out of the buffer container 33 after being mixed with the liquid refrigerant already stored in the buffer container 33, and therefore undesired disturbances in the temperature of the refrigerant flowing downstream of the buffer container 33 can be suppressed.

The three-way valve 34 is provided in a portion of the refrigerant flow path 31 downstream of the portion to which the heat exchanger 40 described below 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 the refrigerant that flows into the first port 341 and flows out from the second port 342, and the flow rate of the refrigerant that flows into the first port 341 and flows out from the third port 343.

The three-way valve 34 constitutes 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 is connected to a portion of the refrigerant flow path 31 upstream of the portion to which the heat exchanger 40 is connected by a bypass flow path 38. More specifically, the bypass flow path 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.

The amount of liquid refrigerant stored in the sealed container 10 can increase or decrease depending on the operating state of the cooling system S1. If the amount of liquid refrigerant stored in the sealed container 10 becomes excessively large, there is an increased risk that the pressure reducing device 20 will suck in the liquid refrigerant. 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 the refrigerant flowing to the sealed container 10.

The three-way valve 34 in this embodiment is a proportional three-way valve. The three-way valve 34 may be a valve that adjusts the opening of the valve body using 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 be an electromagnetic proportional three-way valve or a two-position three-way valve.

As described above, the second outlet 12 in the sealed container 10 is an opening for discharging the liquid refrigerant in the sealed container 10, but 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 vent flow path 28 can allow the liquid refrigerant in the sealed container 10 to flow directly into the buffer container 33. The vent control valve 29 may be opened when the amount of liquid refrigerant stored in the sealed container 10 becomes excessive.

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

The heat exchanger 40 in this embodiment is a liquid-cooled heat exchanger, and is connected to a cooling water flow path 44 through which cooling water flows to cool the refrigerant. The cooling water may be water or another liquid. The heat exchanger 40 may also be an air-cooled heat exchanger.

The heat medium flow device 50 includes a heat medium flow path 51 through which the heat medium flows, and a heat exchange unit 52 and a pump 53 provided in the heat medium flow path 51. In the heat medium flow device 50 of 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 medium flow path 51, and the upstream end 51A and the downstream end 51B of the heat medium flow path 51 are connected to the temperature control target T. In this way, the heat medium flow device 50 circulates the heat medium through the temperature control target T.

More specifically, the heat medium flow path 51 in this embodiment enters the sealed container 10 from the heat medium inlet 15 in the sealed container 10, and then extends to the outside of the sealed container 10 from the heat medium outlet 16. The upstream end 51A, downstream end 51B, and temperature control target T of the heat medium flow path 51 are located outside the sealed container 10. In addition, in the heat medium flow device 50 according to this embodiment, the heat exchange unit 52 is provided in a portion of the heat medium flow path 51 located inside the sealed container 10, that is, the heat exchange unit 52 is disposed inside the sealed container 10. As a result, the heat medium flow path 51 sends the heat medium from the outside of the sealed container 10 to the heat exchange unit 52, and sends the heat medium that has been heat exchanged in the heat exchange unit 52 to the outside of the sealed container 10.

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

The heat exchange unit 52 exchanges heat between the heat medium being passed through and the refrigerant inside the sealed container 10. The heat exchange unit 52 may be composed of a heat exchanger such as a fin tube, or may be composed of a pipe material and form a shell-and-tube type structure together with the sealed container 10. The heat exchange unit 52 may also be a structure that contacts the outer surface of the sealed container 10. In this case, the entire heat medium flow device 50 is disposed outside the sealed container 10.

The pump 53 is provided in a portion of the heat medium flow path 51 located outside the sealed container 10. The type of the pump 53 is not particularly limited, and it may be a non-positive-displacement pump or a positive-displacement pump. The pump 53 includes a motor 53M, such as an AC motor or a brushless DC motor, that is controlled by an inverter. The pump 53 can adjust the amount of liquid drawn in by adjusting the rotation speed of the motor 53M, thereby adjusting the flow rate of the refrigerant flowing through the heat medium flow path 51. More specifically, the rotation 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).

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

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. In detail, 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 medium cooled by the refrigerant, or the temperature of the temperature control target T.

The gas supply device 60 specifically 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 a controller 100 and is controlled by the controller 100. The gas flow control valve 62 may be a valve that adjusts the opening of a valve body 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 be an electromagnetic proportional valve, etc.

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

The cooling system S1 also includes a refrigerant temperature sensor 71 that detects the temperature inside the sealed container 10, a pressure sensor 72 that detects the pressure inside the sealed container 10, a liquid level sensor 73 that detects the liquid level of the liquid refrigerant inside the sealed container 10, and a heat medium temperature sensor 74 that detects the temperature of the heat medium that has been cooled by the refrigerant inside the sealed container 10 and flows out of the sealed container 10.

The refrigerant temperature sensor 71 detects the temperature of the liquid refrigerant in 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 of the sealed container 10 and identify this as the temperature of the refrigerant inside the sealed container 10.

The pressure sensor 72 detects the pressure of the gas phase portion Gf in 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, and irradiates the refrigerant liquid level with light from the top wall of the sealed container 10 and receives the reflected light to calculate the height of the liquid level. However, the liquid level sensor 73 may also be a float type sensor. The heat medium temperature sensor 74 detects the temperature of the heat medium flowing outside the sealed container 10, downstream of the heat exchanger 52 in the heat medium flow path 51. Each sensor (71 to 74) is electrically connected to the controller 100, and the detection results of each sensor are sent to the controller 100.

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

(Controller functional configuration)
Fig. 2 is a block diagram showing the functional configuration of the controller 100. As shown in Fig. 2, the controller 100 has 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 configured, for example, by one computer or by multiple computers. When configured by multiple computers, the multiple functional units may be distributed among the multiple computers.

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

The circulation pump adjustment unit 102 is electrically connected to the circulation pump 32 and controls the operation of the circulation pump 32. More specifically, the circulation pump adjustment unit 102 is connected to the motor 32M of the circulation pump 32 via an inverter. The circulation pump adjustment unit 102 adjusts the frequency of the AC current supplied from the inverter to the motor 32M, thereby adjusting the flow rate of the refrigerant flowing through the refrigerant flow path 31.

The target flow rate of the refrigerant is input and held in the circulation pump adjustment unit 102, for example, by an input device (not shown), and the circulation pump adjustment unit 102 adjusts the rotation speed of the motor 32M of the circulation pump 32 so that the flow rate of the refrigerant matches the target flow rate.

The bypass amount adjustment unit 103 is electrically connected to the three-way valve 34 and controls the operation of the three-way valve 34. In detail, the target liquid level of the liquid refrigerant in the sealed container 10 is input and held in the bypass amount adjustment unit 103, for example, by an input device (not shown). The bypass amount 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 above-mentioned target height as a predetermined 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.

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

In addition, when the liquid level of the liquid refrigerant in the sealed container 10 exceeds a predetermined level, the three-way valve 34 may block the flow of the refrigerant that flows into the first port 341 and flows out from the second port 342, and allow the flow of the refrigerant that flows into the first port 341 and flows out from the third port 343. On the other hand, when the liquid level of the liquid refrigerant in the sealed container 10 falls below a predetermined level, the three-way valve 34 may allow the flow of the refrigerant that flows into the first port 341 and flows out from the second port 342, and block the flow of the refrigerant that flows into the first port 341 and flows out from the third port 343.

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 in the gas suction pump 22 via an inverter. The rotation speed adjustment unit 104 adjusts the frequency of the alternating current supplied from the inverter to the motor 22M, thereby adjusting the flow rate of gas passing through the gas flow path 21 in the pressure reduction device 20.

The target temperature of the heat medium circulated by the heat medium flow device 50 is input and held in the rotation speed adjustment unit 104, for example, by an input device (not shown), and 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 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 medium detected by the heat medium temperature sensor 74 and the target temperature.

In the control example described above, the gas suction pump 22 of the pressure reducing device 20 is controlled so that the temperature of the heat medium matches the target temperature, but instead, the rotation 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 control target T (detection result of a temperature sensor not shown), or the pressure inside the sealed container 10 matches their respective target values.

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 opening of the flow control valve 24 to adjust the flow rate of gas passing through the gas flow path 21 in the pressure reducing device 20.

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 medium cooled by the refrigerant (detection result of the heat medium temperature sensor 74), or the temperature of the temperature control target 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 is controlled so that the temperature of the heat medium coincides with the target temperature and the operating state of the gas suction pump 22 is maintained constant. When the cooling operation actually starts, the temperature or pressure of the refrigerant inside the sealed container 10 may fluctuate. In such a case, 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 medium cooled by the refrigerant, or the temperature of the temperature control target T so that it coincides with the target temperature or target pressure.

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 maintained constant and the opening of the flow control valve 24 may be adjusted, or the opening of the flow control valve 24 may be maintained constant and the operating state of the gas suction pump 22 may be controlled.

The gas supply amount adjustment unit 106 is electrically connected to the gas flow rate adjustment valve 62 and controls the operation of the gas flow rate adjustment valve 62. The gas supply amount adjustment unit 106 adjusts the amount of gas supplied into the sealed container 10 by adjusting the opening degree of the gas flow rate adjustment valve 62.

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 the refrigerant temperature sensor 71), the pressure inside the sealed container 10 (detection result of the pressure sensor 72), the temperature of the heat medium cooled by the refrigerant (detection result of the heat medium temperature sensor 74), or the temperature of the temperature-controlled object T (detection result of a temperature sensor not shown) by controlling the gas flow rate adjustment valve 62 with the gas supply amount adjustment unit 106.

(Refrigerant Composition)
Next, the refrigerant circulated in the cooling system S1 will be described. As described above, in this embodiment, the refrigerant is, for example, a substance that becomes liquid under atmospheric pressure and at a standard environmental temperature (for example, 25°C), and when expanded from this state in an environment of, for example, 0.1 atmospheric pressure, the temperature becomes -5°C or lower, and preferably, when expanded in an environment of 0.01 atmospheric pressure, the temperature becomes -30°C or lower. In addition, the refrigerant is preferably a low environmental load refrigerant with a global warming potential (GWP) of 10 or less.

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 medium circulated by the heat medium flow device 50 may also be HFO-1336mzz-Z. More specifically, the refrigerant may be Opteon SF33 (TM) manufactured by Mitsui-Chemours Fluoroproducts, Inc.

Figure 3 is a pH diagram of HFO-1336mzz-Z. When HFO-1336mzz-Z is depressurized from a state (St1) of approximately 33°C, close to room temperature, at approximately 0.100 MPa, close to atmospheric pressure, to 0.0149 MPa, the temperature drops to approximately -10°C (St2). When it is depressurized to 0.001 MPa, the temperature drops to approximately -50°C or lower. Then, when it absorbs a certain amount of heat from the state St2 where it has been cooled to approximately -10°C, it evaporates (St3), and when it expands from this state St3 to approximately 0.100 MPa, close to atmospheric pressure, it rises in temperature to approximately 50°C, which is higher than room temperature, while remaining in the gas phase (St4). Then, when it is cooled from state St4 to room temperature, it condenses into a gas-liquid mixed phase and is cooled to approximately 33°C.

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

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

(motion)
An example of the operation of the cooling system S1 will now be described.

First, in the cooling system S1, the target temperature of the heat medium circulated by the heat medium circulating 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 circulating device 30 and the pump 53 of the heat medium circulating 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 becomes a predetermined level. Then, after the liquid level of the liquid refrigerant in the sealed container 10 matches the predetermined level, the three-way valve 34 blocks the flow of the refrigerant that flows into the first port 341 and flows out of the second port 342, and allows the flow of the refrigerant that flows into the first port 341 and flows out of the third port 343. That is, a state is created in which the liquid refrigerant does not flow from the refrigerant circulating device 30 into the sealed container 10.

Then, the pressure reducing device 20 is driven, and the pressure inside the sealed container 10 is reduced by the pressure reducing device 20 to a pressure lower than atmospheric pressure. 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 medium temperature sensor 74 matches the target temperature. Then, after the temperature detected by the heat 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 of the flow control valve 24, and the opening of the gas flow rate adjustment valve 62 of the gas supply device 60 is controlled to maintain the target temperature. This completes the startup operation. In the state after the rotation speed of the motor 22M of the gas suction pump 22 is adjusted so that the temperature detected by the heat 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 and the refrigerant flow environment in the heat exchanger 40 are set to a pressure higher than the pressure inside the sealed container 10, for example, 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 strictly atmospheric pressure, and may be a pressure slightly lower than atmospheric pressure.

After that, the heat medium circulated by the heat medium circulating device 50 is shifted to a state in which it cools the temperature-controlled object T. The refrigerant flows out of the sealed container 10, is cooled by the cooling section 25 and the heat exchanger 40, and then flows back into the sealed container 10. This allows the heat medium to be continuously cooled by the refrigerant.

In other words, to explain the operating state of the cooling system S1 using FIG. 3, the refrigerant that has absorbed the heat of the heat medium flows out of the sealed container 10, and is cooled by the cooling section 25 and the heat exchanger 40, and transitions from state St4 to state St1 in FIG. 3. The refrigerant is then depressurized by flowing into the sealed container 10, and transitions to state St2. The refrigerant then transitions from state St2 to state St3 by exchanging heat with the heat medium in the sealed container 10. The refrigerant then transitions from state St3 to state St4 by flowing out of the pressure reducing device 20 from the sealed container 10. The refrigerant is then cooled by the cooling section 25 and the heat exchanger 40, and transitions from state St4 to state St1. As a result, the heat medium is continuously cooled by the refrigerant.

The cooling system S1 according to the first embodiment described above includes a sealed container 10 including a first outlet 11 and an inlet 13 for storing a liquid refrigerant, a pressure reducing device 20 connected to the first outlet 11 and for adjusting 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 including a refrigerant flow path 31 connected to the pressure reducing device 20 and the inlet 13 for causing the liquid refrigerant 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, and the temperature control target T is cooled by the refrigerant in the sealed container 10.

With this type of cooling system S1, it becomes possible to use substances that have not been used in conventional refrigeration methods as refrigerants in a heat cycle, or to expand the range of substances that can be used as refrigerants in a heat cycle.

In other words, as described above, in this embodiment, as an example, a substance that becomes liquid under atmospheric pressure and at a standard environmental temperature (e.g., 25°C) and that becomes -5°C or lower when expanded from this state in an environment of, for example, 0.1 atmospheric pressure can be used as the refrigerant. In contrast, if the above substance is used in a vapor compression refrigeration cycle that has been widespread up to now, for example, the compressor will compress the liquid, so the compressor will not function properly and the substance will not evaporate in the evaporator. Therefore, the above refrigerant is not suitable for a vapor compression refrigeration cycle. In contrast, the cooling system S1 does not use compression, but rather reduces the pressure of the above refrigerant in the sealed container 10, making it possible to cool the heat medium, and the heat of the heat medium can be released from the cooling unit 25 and the heat exchanger 40, thereby realizing a heat cycle. Therefore, according to this embodiment, it becomes possible to use a substance that has not been used in conventional refrigeration methods as a refrigerant for a heat cycle, or the range of substances that can be used as a refrigerant for a heat cycle can be expanded. In addition, in this embodiment, the decompression device 20 is provided with the cooling unit 25, so that heat is released between the cooling unit 25 and the heat exchanger 40. On the other hand, a configuration may be adopted in which heat is dissipated only by the cooling unit 25 without providing a heat exchanger 40, or heat may be dissipated only by the heat exchanger 40 without providing a cooling unit 25.

As described above, the cooling system S1 is capable of using, for example, HFO-1336mzz-Z, which has a GWP of 2 and is non-flammable, as a refrigerant. This makes it possible to achieve a cooling operation with a low GWP and ensured safety, which is currently not possible with vapor compression refrigeration cycles. No other cooling method is known that provides such a low GWP, low environmental impact, and ensures safety. Therefore, the realization of such a cooling system S1 has the potential to greatly contribute to protecting the global environment. In addition, because the cooling system S1 does not use a compressor, the situation in which lubricating oil leaks into the refrigerant is suppressed, which is also beneficial in this respect.

In addition, this embodiment has various features to operate the cooling system S1 economically and stably.

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 to draw 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 to store the gas flowing out from the downstream end 21B. This makes it easier to vaporize the gas in the reservoir tank 23, and prevents the refrigerant in gaseous state from returning to the sealed container 10 by the refrigerant circulation device 30.

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 prevents the refrigerant in a gaseous state from returning to the sealed container 10 by the refrigerant circulation device 30.

The refrigerant circulation device 30 further includes a buffer container 33 that is provided in the refrigerant flow path 31 so as to form a part of the refrigerant flow path 31 and stores liquid refrigerant. The gas stored in the reservoir tank 23 or liquid refrigerant that is at least partially liquefied from the gas is caused to flow 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 and then flow out of the buffer container 33. This can prevent undesirable temperature disturbances of the refrigerant flowing downstream of the buffer container 33.

The refrigerant circulation device 30 also includes a three-way valve 34 that is provided in a portion of the refrigerant flow path 31 downstream of the portion where the heat exchanger 40 is connected, and includes 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 is also connected to a portion of the refrigerant flow path 31 upstream of the portion where the heat exchanger 40 is connected (the buffer container 33 in this embodiment) by a bypass flow path 38.

This allows the cooling system S1 to operate stably, improving the accuracy of temperature control. For example, if the amount of liquid refrigerant stored in the sealed container 10 becomes excessively large, there is an increased risk that the pressure reducing device 20 will suck in the liquid refrigerant. 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. In such a case, for example, the three-way valve 34 can prevent a situation in which the amount of liquid refrigerant in the sealed container 10 becomes excessive by reducing or blocking the flow rate of the refrigerant flowing to the sealed container 10 side.

Second Embodiment
Next, a cooling system S2 according to a second embodiment will be described with reference to Fig. 4. Note that, among the components in this embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and duplicated descriptions will be omitted.

This embodiment differs from the first embodiment in that the vent passage 28 connecting the sealed container 10 and the buffer container 33 and the vent control valve 29 on the vent passage 28 are not provided. The cooling system S2 according to this second embodiment also provides the same effects as the first embodiment. Furthermore, according to this embodiment, the device configuration can be simplified.

Third Embodiment
Next, a cooling system S3 according to a third embodiment will be described with reference to Fig. 5. Note that, among the components in this embodiment, the same components as those in the first and second embodiments are denoted by the same reference numerals, and duplicated descriptions will be omitted.

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 disposed inside the buffer container 33. The heat exchanger 40 may be configured to contact the outer wall of the buffer container 33, or may be connected to the upstream or downstream part of the buffer container 33 in the refrigerant flow path 31.

In addition, in this embodiment, a return amount adjustment valve 80 is provided in the refrigerant flow path 31. The return amount 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. In detail, the return amount 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 the liquid level of the liquid refrigerant in the sealed container 10 is maintained at a predetermined height, for example. The return amount adjustment valve 80 may be an opening/closing valve or a proportional valve.

Below, an example of the operation of the cooling system S3 is described.

First, in the cooling system S3, the target temperature of the heat medium circulated by the heat medium circulating 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 medium circulating device 50 is driven. At this time, the return amount adjustment valve 80 is controlled so that the liquid level of the liquid refrigerant in the sealed container 10 becomes a predetermined level. In this embodiment, when the return amount adjustment valve 80 opens, the liquid refrigerant naturally flows into the sealed container 10 due to its own weight, but a circulation pump 32 may also be provided. Then, after the liquid level of the liquid refrigerant in the sealed container 10 matches the predetermined level, the return amount adjustment valve 80 is closed.

Then, the pressure reducing device 20 is driven, and the pressure in the sealed container 10 is reduced by the pressure reducing device 20 to a pressure lower than atmospheric pressure. 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 medium temperature sensor 74 matches the target temperature. After the temperature detected by the heat 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 of the flow control valve 24, and the opening of the gas flow rate adjustment valve 62 of the gas supply device 60 is controlled to maintain the target temperature. This completes the start-up operation. In the state after the rotation speed of the motor 22M of the gas suction pump 22 is adjusted so that the temperature detected by the heat medium temperature sensor 74 matches the target temperature, the pressure in the sealed container 10 is reduced by the pressure reducing device 20 to a pressure lower than atmospheric pressure, 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 in the sealed container 10, for example, atmospheric pressure. However, the refrigerant flow environment in the refrigerant circulation device 30 does not have to be strictly atmospheric pressure, and may be slightly lower than atmospheric pressure.

The cooling system S3 according to the third embodiment can achieve the same effects as the first embodiment and can simplify the device configuration.

<Fourth embodiment>
Next, a cooling system S4 according to a fourth embodiment will be described with reference to Fig. 6. Note that, among the components in this embodiment, the same components as those in the first to third embodiments are denoted by the same reference numerals, and duplicated descriptions will be omitted.

This embodiment is further simplified by removing the buffer vessel 33 from the refrigerant circulation device 30 in the third embodiment and not using the heat exchanger 40. The cooling system S4 can be operated in the manner described in the third embodiment. This embodiment is beneficial in terms of simplifying the device.

Although the 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-described embodiments.

Claims

a container including an outlet and an inlet and configured to store a liquid refrigerant;
a pressure reducing device connected to the outlet and configured to adjust the pressure in the container to a pressure lower than atmospheric pressure by sucking gas from the container through the outlet;
a refrigerant circulation device including a refrigerant flow path connected to the pressure reducing device and the inlet, the refrigerant being liquefied from the gas sucked from the container by the pressure reducing device and flowing into the container through the inlet,
A cooling system that cools a temperature-controlled object using the refrigerant in the container.
The pressure reducing device is
A gas flow path connected to the outlet;
a gas suction pump provided in the gas flow path and configured to suck the gas from the container into the gas flow path;
a reservoir tank connected to the gas flow path and configured to store the gas flowing out of the gas flow path and/or the refrigerant in a liquid state liquefied from the gas,
The cooling system of claim 1 , wherein the coolant flow path connects to the reservoir tank.
The cooling system of claim 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 flow path into the liquid refrigerant and stores the liquid refrigerant.
The cooling system of claim 3, wherein the refrigerant circulation device further includes a circulation pump provided in the refrigerant flow path and drawing the liquid refrigerant from the reservoir tank into the refrigerant flow path.
The cooling system according to claim 3, wherein the pressure reducing device further includes a cooling section that cools a portion of the gas flow path downstream of the gas suction pump and/or the reservoir tank.
The refrigerant circulation device further includes a buffer container that is provided in the refrigerant flow path so as to form a part of the refrigerant flow path and stores the refrigerant in a liquid state.
The cooling system of claim 3 , wherein the liquid refrigerant drawn from the reservoir into the refrigerant flow path passes through the buffer vessel before entering the vessel.
The cooling system further includes a heat exchanger connected to the refrigerant flow path and configured to cool the liquid refrigerant flowing through the refrigerant flow path.
The cooling system according to claim 6 , wherein the buffer container is provided in a portion of the refrigerant flow path upstream of a portion to which the heat exchanger is connected.
The cooling system of claim 6, wherein the reservoir tank is disposed above the buffer container.
The gas suction pump is configured to suck the gas by rotation of a motor,
3. The cooling system according to claim 2, wherein the gas suction pump adjusts a rotation speed of the motor in accordance with a temperature in the container, a pressure in the container, a temperature of the heat medium cooled by the refrigerant, or a temperature of the temperature-controlled object.
a flow control valve for controlling a flow rate of the gas flowing through the gas flow path by adjusting an opening degree of the flow control valve provided in a portion of the gas flow path upstream or downstream of the gas suction pump;
3. The cooling system according to claim 2, wherein the flow control valve adjusts its opening degree in accordance with a temperature in the container, a pressure in the container, a temperature of the heat medium cooled by the refrigerant, or a temperature of the temperature-controlled object.
A gas supply device for supplying gas into the container is further provided,
The cooling system according to claim 10, wherein the gas supply device adjusts the amount of the gas supplied into the container in accordance with a temperature in the container, a pressure in the container, a temperature of the heat medium cooled by the refrigerant, or a temperature of the temperature-controlled object.
The cooling system further includes a heat exchanger connected to the refrigerant flow path and configured to cool the liquid refrigerant flowing through the refrigerant flow path.
the refrigerant circulation device is provided in a portion of the refrigerant flow path downstream of a portion 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 a flow rate of the refrigerant flowing into the first port and flowing out from the second port, and a 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 with a flow path between the first port and the second port,
The cooling system according to claim 1 , wherein the third port and a portion of the refrigerant flow path upstream of a portion to which the heat exchanger is connected are connected by a bypass flow path.
the three-way valve, when a liquid level of the refrigerant in a liquid state in the container exceeds a predetermined level, reduces a flow rate of the refrigerant flowing into the first port and flowing out of the second port and increases a flow rate of the refrigerant flowing into the first port and flowing out of the third port;
13. The cooling system of claim 12, wherein the three-way valve increases a flow rate of the refrigerant flowing into the first port and flowing out of the second port and decreases a flow rate of the refrigerant flowing into the first port and flowing out of the third port when a liquid level of the refrigerant in the container falls below a predetermined level.
when a liquid level of the refrigerant in a liquid state in the container exceeds a predetermined level, the three-way valve blocks the flow of the refrigerant flowing into the first port and flowing out of the second port and allows the flow of the refrigerant flowing into the first port and flowing out of the third port;
13. The cooling system of claim 12, wherein the three-way valve allows the refrigerant to flow into the first port and flow out of the second port and blocks the flow of the refrigerant to flow into the first port and flow out of the third port when a liquid level of the refrigerant in the container falls below a predetermined level.
The heat transfer medium supply device further includes a heat transfer medium flow path for allowing the heat transfer medium to flow.
the heat medium flow path is disposed in the container and includes a heat exchange portion that exchanges heat between the heat medium and the refrigerant,
The cooling system according to claim 1 , wherein the heat medium flow path feeds the heat medium from the outside of the container to the heat exchange section, and feeds the heat medium that has exchanged heat in the heat exchange section to the outside of the container.
The cooling system according to claim 1, wherein the refrigerant is a substance having a boiling point of 30°C or higher under atmospheric pressure.
The cooling system of claim 16, wherein the refrigerant has a GWP of 10 or less.
The cooling system of claim 17, wherein the refrigerant is HFO-1336mzz-Z.