JPH1019305A - Cooling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need of forced cooling means like a freezing cycle by providing a refrigerant naturally circulating in a closed circuit consisting of an air conditioner, a vapor pipe, a condenser, and a liquid pipe, and cooling the condenser with fresh air. SOLUTION: A refrigerant such as fluorocarbon gas is naturally circulated in a closed circuit consisting of an air conditioner 2, a vapor pipe 11, a condenser 3 and a liquid pipe 12. In the condenser 3, the refrigerant is cooled with fresh air, condensed and liquefied, and returns to the air conditioner 2 through a liquid level adjuster 14. With repetition of a series of operation produced heat in a room to be air conditioned is discharged to the fresh air. When there is a large temperature difference between fresh air temperature and the room to be air conditioned as in winter or when the amount of heat produced in the room is small, in the condenser 3 cooling of the refrigerant is achieved by operation of a fan 33. In summer, cooling water is supplied to a heat exchange part 31 with both the fan 33 and a pump 36 to promote the cooling of the refrigerant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling system for cooling a space or a room in which an air conditioner is installed, and more particularly to a cooling system in which a heating device such as an electronic device or a mechanical device is installed. The present invention relates to a cooling system for cooling a space.

[0002]

2. Description of the Related Art Usually, a space in which a large number of electronic devices are installed, a machine room, or the like is heated to a higher temperature (for example, 40 ° C. or more) than the surrounding space or the outside air temperature due to heat generated by these devices. I have. Therefore, the space is not only unpleasant for humans, but also has a bad influence such as shortening the life of various devices installed in the space. As a method for alleviating such a situation, a method is generally used in which an air conditioning system using a refrigeration cycle or the like is installed in the space and heat generated in the room is released to the outside.

However, a cooling method using such a refrigeration cycle is not preferable because a large amount of energy such as electric power must be used to operate the compressor. In particular, when cooling a plurality of spaces, not only is the amount of energy used enormous, but also there are drawbacks such as requiring a large amount of space to install a large number of outdoor units. In addition, the running cost is enormous, which has the disadvantage of increasing the economic burden on the user.

On the other hand, as a means for solving the above-mentioned drawbacks, there has been proposed an air conditioning system utilizing a natural circulation function of a refrigerant as disclosed in Japanese Patent Publication No. 8-6940. This system is an air conditioning system in which a cold heat source is provided at a high place of a building, an air conditioner is provided at a lower place than the cold heat source, and the cold heat source and the air conditioner are connected by a gravity heat pipe. Then, the first condenser section cooled by the cold heat source, the second condenser section cooled by the outside air, and the first condenser section and the second condenser section are selectively switched to change the circulation path of the refrigerant gas. And a switching valve.

[0005] The gravity type heat pipe uses a refrigerant such as chlorofluorocarbon to absorb the heat load of the room to be air-conditioned by a heat exchanger in the air conditioner, thereby changing the refrigerant from a liquid phase to a gas phase, and To rise. Then, the gas phase refrigerant reaches the first condensing section cooled by the cold heat source or the second condensing section cooled by the outside air. The gas-phase refrigerant is cooled and condensed in any one of these condensing parts, becomes a liquid phase, descends in the heat pipe by gravity, and returns to the air conditioner. Whether the refrigerant circulates through the heat pipe through the first condensing section or circulates through the heat pipe through the second condensing section is selectively changed by a switching valve, and the heat load on the air-conditioned room side is reduced. If sufficiently large, the refrigerant passes through the first condensing section, and if the heat load is not very large, the refrigerant passes through the second condensing section.

In the above air conditioning system, the operation of the room to be air conditioned is performed by the natural circulation of the refrigerant. Therefore, even if there are a plurality of air conditioned rooms, the cold heat source can be installed at one location such as a rooftop to save space. . In addition, since the condensing capacity of the condensing unit can be selectively switched according to the air conditioning load, when the air conditioning load is small, cooling is performed without operating the cold heat source, and energy saving is improved.

[0007]

However, in the case of this air-conditioning system as well, when it is considered as a means for releasing the heat generated by various devices installed in a room or space, when the air-conditioning load is large, it is mainly used. Since a cold heat source such as a refrigerator must be operated, energy saving is not sufficient. Further, since two condensers for cooling the refrigerant evaporated in the indoor unit are required, an extra space for installing the second condenser, which is a cold heat source, is required. A switching valve and control means for selectively switching between the cases were required.

SUMMARY OF THE INVENTION The present invention has been made in order to effectively solve the above-mentioned problems, and an object of the present invention is to cool a heating space in which electronic devices and various mechanical devices are installed by using a forced cooling system such as a refrigeration cycle. It uses a small amount of energy without using a typical cold heat source, reduces the economic burden on the user, keeps the equipment installation area compact, and switches the flow path by operating the switching valve. It is an object of the present invention to provide a cooling system which does not perform any control. Another object of the present invention is to provide an effective cooling system that is excellent in energy saving and economy by using a cooling heat source as an auxiliary.

[0009]

In order to achieve the above object, a cooling system according to the present invention is provided with at least one air conditioner having at least a heat exchanger and a higher position than the air conditioner. A single condenser, a steam pipe connecting a refrigerant outlet of the air conditioner and a refrigerant inlet of the condenser, a liquid pipe connecting a refrigerant inlet of the air conditioner and a refrigerant outlet of the condenser, A closed circuit including an air conditioner, a steam pipe, a condenser, and a liquid pipe has a refrigerant that circulates naturally, and the condenser is cooled by outside air.

The condenser preferably includes a fan for forcibly supplying outside air to the condenser heat exchange section, and a cooling water circulation mechanism for supplying cooling water to the condenser heat exchange section. The cooling system according to the present invention performs heat transport by naturally circulating the refrigerant without using external power due to the phase change and the action of gravity of the refrigerant composed of Freon or the like. The refrigerant in the system absorbs the heat load of the room to be conditioned, which has become hotter than the outside air, in the heat exchanger in the air conditioner, and changes from a liquid phase to a gas phase. The vaporized refrigerant rises in the steam pipe and is sent to the condenser. In the condenser, the gas-phase refrigerant is cooled by outside air and condensed, descends through the liquid pipe by gravity, and returns to the air conditioner.

When the temperature of the outside air is low, such as in winter, or when the heat load is small, the cooling of the refrigerant in the condenser is
This is done by operating a fan installed in the condenser. When the temperature of the outside air is high, such as in summer, or when the heat load is large, a fan installed in the condenser is operated, and cooling water is sprayed on the condenser using forced circulation means such as a pump. Thereby, the cooling of the refrigerant is performed by using the cooling function of the outside air and the evaporation / cooling function of the water.

In the cooling system of the present invention, heat is transported from the room to be air-conditioned to the outside air by the natural circulation of the refrigerant. Can be reduced. Further, since a cooling source by forced means such as a refrigerator or a heat storage system is not required, the installation area of the device can be reduced. In addition, a cold heat source (condenser)
Since there is only one, a cooling system can be constructed with a simple configuration without using a switching valve and the like, and control can be simplified.

In the cooling system of the present invention, in order to increase the cooling efficiency of the condenser, a loop is provided between the condenser and the cooling tower via a pump so as to reduce the temperature of the cooling water. It can be configured to be even lower. In the cooling tower, the temperature of the cooling water is lowered by blowing air to a cooling tower heat exchange section through which the cooling water circulates.

In the present invention, if necessary, an auxiliary chiller is connected to the cooling water circulating mechanism of the condenser for lowering the temperature of the cooling water, and a pipe is formed in a loop through a pump. In the water cooler, the temperature of the cooling water may be forcibly reduced by using a refrigeration cycle. When the temperature of the outside air is low, such as in winter, or when the heat load is small, cooling of the refrigerant in the condenser is performed by operating a fan installed in the condenser. When the temperature of the outside air is high, such as in summer, or when the heat load is large, the fan installed in the condenser is operated, and the cooling air is blown to the condenser using forced circulation means such as a pump. The cooling of the refrigerant is performed using the cooling action of the water and the evaporation / cooling action of water. At this time, by operating the cooling tower or the water cooler connected to the cooling water circulation mechanism, the temperature of the cooling water can be lowered, so that the air-conditioned room can be efficiently moved even when the heat load is particularly large, such as during the daytime in summer. It becomes possible to cool.

In the present invention, the outside air sensor detects the outside air sensor for measuring the outside air temperature, the refrigerant temperature sensor for detecting the temperature of the refrigerant in the cooling system, and the refrigerant temperature detected by the refrigerant temperature sensor. Control means for operating the cooling water circulation mechanism only when the value obtained by subtracting the outside air temperature is equal to or less than a predetermined value may be further provided.

Further, according to the present invention, an outside air sensor for measuring the outside air temperature, a pressure sensor for detecting the pressure of the refrigerant vapor in the condenser, and a saturation temperature corresponding to the pressure of the refrigerant vapor detected by the pressure sensor Therefore, a control means for operating the cooling water circulation mechanism only when a value obtained by subtracting the outside air temperature detected by the outside air sensor is equal to or less than a predetermined value may be provided.

In the present invention using such control means,
The use of the cooling water in the cooling system is determined when the difference between the outside air temperature and the refrigerant liquid temperature or the difference between the saturation temperature corresponding to the refrigerant vapor pressure and the outside air temperature becomes smaller than a certain value. By using water, the system can be operated more effectively. The set values of the temperature difference and the pressure difference may be changed according to the season, the internal load, and the like.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a cooling system according to the present invention will be described in detail based on an embodiment shown in the drawings. First Embodiment FIG. 1 is a schematic diagram of a cooling system according to an embodiment of the present invention.

As shown in FIG. 1, a cooling system 1 according to the present embodiment includes a plurality of air conditioners 2, a single condenser 3 installed at a higher position than the air conditioners 2, And a liquid pipe 12 connecting the refrigerant inlet of the air conditioner 2 and the refrigerant outlet of the condenser 3 to each other.

These air conditioner 2, steam pipe 11, condenser 3
A refrigerant such as Freon gas naturally circulates in the closed circuit constituted by the liquid tube 12 and the liquid tube 12.
The air conditioner 2 is provided with a heat exchanger 21 and a fan 22, and is installed in one or more air-conditioned rooms. In FIG. 1, reference numeral 13 denotes a liquid receiver installed in the middle of the liquid pipe, and reference numeral 14 denotes a liquid level controller for the liquid refrigerant installed in each air conditioner 2.

The condenser 3 disposed at a high place such as the roof of a building has a cylindrical cover 32 surrounding the heat exchange section 31. In addition, a fan 33 is mounted on the upper part of the cover 32 so that the outside air flows from the bottom to the top in the heat exchange part 31, and a water reservoir for storing cooling water for cooling is provided below the air inlet 34. 35 are provided. Pool 3
5 is connected to a pump 36 for circulating the cooling water and a pipe 37 for sending the cooling water to the upper part of the heat exchange unit 31. A blowout section 38 for supplying cooling water to the heat exchange section 31 is mounted above the pipe 37.

The liquid pipe 12 is provided with a valve 40 such as an electromagnetic valve. This valve 40 closes the valve 40 when the outside air temperature becomes higher than the refrigerant operating temperature (saturation temperature), for example, to prevent excess refrigerant liquid from flowing into the evaporator 2. If the evaporator is filled with the refrigerant liquid, the evaporator may not operate at the next operation, so that this is prevented.

According to the cooling system 1 of this embodiment,
The heat generated from the heat-generating devices installed inside the room to be air-conditioned is absorbed by the air conditioner 2. In the air conditioner 2, the refrigerant in the heat exchanger 21 absorbs heat and evaporates to form a vapor pipe 11.
To the condenser 3 installed at a high place. In the condenser 3, the refrigerant is cooled by outside air and condensed and liquefied, and returns to the air conditioner 2 via the liquid receiver 13 and the liquid level controller 14 by gravity. By repeating this series of operations, heat generated in the room to be conditioned is released to the outside air.

As in winter, when the difference between the outside air temperature and the temperature of the room to be conditioned is large (the temperature of the room to be conditioned is higher than the outside air temperature), or when the amount of heat generated in the room to be conditioned is small, the condenser 3 In the embodiment, the cooling of the refrigerant is performed by operating the fan 33 provided at the upper part. On the other hand, when the difference between the outside air temperature and the temperature of the room to be air-conditioned is small as in summer, or when the amount of heat generated in the room to be air-conditioned is large, the pump 36 is operated at the same time as the fan 33 is turned on to cool the cooling water. Exchange part 3
1 to promote cooling of the refrigerant. At this time, a part of the cooling water evaporates by removing heat from the refrigerant, and in that case, an amount of makeup water corresponding to the amount of evaporated water is supplied from a makeup water supply port (not shown). In the makeup water supply port,
It is preferable to use a simple mechanism such as a float valve directly connected to tap water.

According to the cooling system of this embodiment, a large amount of energy such as a refrigeration cycle is used because the air-conditioned room is cooled by the outside air or the cooling water whose temperature is lower than that of the room to be air-conditioned. Cooling can be efficiently performed without using a cold heat source. Therefore, it is possible to suppress a decrease in the life of the equipment installed in the room to be air-conditioned, and
The economic burden on the user can be reduced.

Second Embodiment In the above-described embodiment, the circulation of the cooling water of the condenser 3 is performed in the order of the water reservoir 35 → the pump 36 → the blow-out portion 38 → the water reservoir 35. Instead, for example, another cooling tower 4 may be installed as shown in FIG. In the present embodiment, the cooling water is stored in the sump 35 → the pump 36 → the cooling tower 4.
The air is circulated in the order of → the blowing section 38 → the water storage section 35. In the cooling tower 4, the temperature of the cooling water is reduced by blowing air using a fan 52 to the cooling tower heat exchange unit 50 in which the cooling water circulates.

In this embodiment, the cooling water is supplied to the heat exchanging section 31.
Before being supplied to the cooling tower 4, the cooling is performed by the cooling tower 4, so that the cooling can be effectively performed even when the calorific value of the room to be air-conditioned is further increased. Since other configurations and operations of the air conditioning system 1a of the embodiment shown in FIG. 2 are the same as those of the air conditioning system 1 of FIG. 1, the same members are denoted by the same reference numerals.
Their description is omitted.

In this embodiment, for example, an outside air sensor 60 for measuring the outside air temperature and a refrigerant temperature sensor 62 for detecting the temperature of the refrigerant in the cooling system are connected to the control means 64.
The following control may be performed. That is, the refrigerant temperature t _r detected by the refrigerant temperature sensor 62, outside air sensor 6
A value obtained by subtracting the outside air temperature t ₀ detected at ₀ (t _r -t ₀ )
Is sent from the control means 64 only when the value is equal to or less than the predetermined value x, and the pump 36 and the fan 52 are operated,
Activate the cooling water circulation mechanism. The refrigerant temperature sensor 6
2 is an air conditioner 2 and a steam pipe 1 if the refrigerant temperature can be measured.
1, may be mounted at any position in the closed circuit constituted by the condenser 3 and the liquid pipe 12, but is preferably in a liquid phase. The control means 64 is constituted by, for example, a microcomputer, a personal computer, or a general-purpose computer. The temperature sensors 60 and 62 are configured by, for example, thermocouples or the like.

In the present embodiment using such control means 64, the determination of the use of the cooling water in the cooling system 1a is made as follows.
Carried out by the difference between the temperature t _r of the outside air temperature t ₀ and the refrigerant fluid, that this difference is to use only the cooling water when it becomes smaller than a predetermined value, and can be operated more effectively system Become. The set value of the temperature difference may be changed according to the season, the internal load, or the like. For example, the predetermined value x =
3-10 ° C.

Since the refrigerant temperature is the saturation temperature of the refrigerant, the pressure sensor 66 detects the refrigerant vapor pressure during the refrigerant closed cycle of the cooling system, and converts the pressure to the saturation temperature by the control means 64. However, the same control as described above can be performed. That is, the pump 36 and the fan 52 are driven only when a value obtained by subtracting the outside air temperature detected by the outside air sensor 60 from the saturation temperature corresponding to the pressure of the refrigerant vapor detected by the pressure sensor 66 is equal to or less than a predetermined value. Then, the cooling water circulation mechanism is activated. In addition,
The pressure sensor 66 is constituted by, for example, a piezoelectric element or the like,
As long as it is a position where the refrigerant vapor pressure can be detected, it may be installed at any position of the piping or the equipment in the refrigerant closed circuit.

Third Embodiment FIG. 3 is a schematic diagram of a cooling system according to another embodiment of the present invention. The cooling system 1b shown in FIG. 3 is a modification of the cooling system 1b shown in FIG.

In the present embodiment, a water cooler 4a is used instead of the cooling tower 4 shown in FIG. In the water cooler 4a, it is possible to forcibly lower the temperature of the cooling water using a refrigeration cycle. In the cooling system 1b according to the present embodiment, members common to the cooling system 1b of the embodiment illustrated in FIG. 2 are denoted by common reference numerals, and a description thereof is partially omitted.

In the present embodiment, when the difference between the outside air temperature and the temperature of the room to be conditioned is large, as in winter, or when the amount of heat generated in the room to be conditioned is small, the condenser 33 is provided with the fan 33 provided at the top. The operation cools the refrigerant. On the other hand, when the difference between the outside air temperature and the temperature of the room to be air-conditioned is small as in summer, or when the amount of heat generated in the room to be air-conditioned is large, the pump 36 is operated at the same time as the fan 33 is turned on to cool the cooling water. By supplying the refrigerant to the exchange unit 31, cooling of the refrigerant is promoted. At this time, a part of the cooling water evaporates by removing heat from the refrigerant, and in that case, an amount of makeup water corresponding to the amount of evaporated water is supplied from a makeup water supply port (not shown). It is preferable to use a simple mechanism such as a float valve directly connected to tap water for the makeup water supply port.

Further, when the amount of heat generated in the room to be air-conditioned is large as in the daytime in summer and the refrigerant cannot be sufficiently cooled only by cooling with the outside air (and cooling water that only circulates), the chiller 4a Is used to cool the cooling water to compensate for the lack of cooling capacity due to outside air.

According to the cooling system of this embodiment, the room to be conditioned is cooled by the outside air or the cooling water whose temperature is lower than that of the room to be conditioned with a simple structure. Cooling can be performed effectively without using energy. Therefore, it is possible to suppress a decrease in the life of the equipment installed in the room to be air-conditioned, and
The economic burden on the user can be reduced.

Further, a chiller 4 is provided in the middle of the cooling water circulation mechanism.
Since a is provided, cooling can be performed effectively even when the amount of heat generated in the room to be air-conditioned is even larger. In this embodiment, similarly to the second embodiment, for example, an outside air sensor 60 for measuring the outside air temperature and a refrigerant temperature sensor 62 for detecting the temperature of the refrigerant in the cooling system are connected to the control means 64, and Such control may be performed.

[0037] That is, the refrigerant temperature t _r detected by the refrigerant temperature sensor 62, a value obtained by subtracting the outdoor air temperature t ₀ detected by the outside air sensor 60 (t _r -t ₀₎ is, only when it is less than the predetermined value x , A signal is sent from the control means 64 and the pump 3
6 and the water cooler 4a are operated to operate the cooling water circulation mechanism. The refrigerant temperature sensor 62 may be mounted at any position in a closed circuit formed by the air conditioner 2, the steam pipe 11, the condenser 3, and the liquid pipe 12, as long as the refrigerant temperature can be measured. The control means 64 is constituted by, for example, a microcomputer, a personal computer, or a general-purpose computer. The temperature sensors 60 and 62 are configured by, for example, thermocouples or the like.

In this embodiment using such a control means 64, the determination of the use of the cooling water in the cooling system 1b is made as follows.
Carried out by the difference between the temperature t _r of the outside air temperature t ₀ and the refrigerant fluid, that this difference is to use only the cooling water when it becomes smaller than a predetermined value, and can be operated more effectively system Become. The set value of the temperature difference may be changed according to the season, the internal load, or the like. For example, the predetermined value x =
3-10 ° C.

Since the refrigerant temperature is the saturation temperature of the refrigerant, the pressure sensor 66 detects the refrigerant vapor pressure during the refrigerant closed cycle of the cooling system, and converts the pressure to the saturation temperature by the control means 64. However, the same control as described above can be performed. That is, only when the value obtained by subtracting the outside air temperature detected by the outside air sensor 60 from the saturation temperature corresponding to the pressure of the refrigerant vapor detected by the pressure sensor 66 is equal to or less than a predetermined value, the pump 36 and the chiller 4a are turned off. It drives and activates the cooling water circulation mechanism. In addition,
The pressure sensor 66 is constituted by, for example, a piezoelectric element or the like,
As long as it is a position where the refrigerant vapor pressure can be detected, it may be installed at any position of the piping or the equipment in the refrigerant closed circuit.

The present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the present invention. For example, in each of the above embodiments, the supply amount of the refrigerant to the air conditioner is adjusted using the liquid level controller 14, but in the present invention, the refrigerant liquid level of the heat exchanger is detected inside the air conditioner. For detecting the liquid level may be provided. In this case, the opening of a control source (such as a valve) installed in the liquid pipe is adjusted by a signal from the liquid level detecting means. In the present invention, the control may be performed by another method. Further, a system in which a plurality of the present systems are arranged in parallel according to the height and size of the building may be constructed. Further, a water cooler and a cooling tower may be provided side by side.

Further, the cooling water circulation mechanism is not limited to the above-described embodiment.
Needless to say, anything that satisfies the function can be used.

[0042]

As described above, according to the present invention, since heat is transferred from the room to be air-conditioned to the outside air by the natural circulation of the refrigerant, no forced cooling means such as a refrigeration cycle is required. . Therefore, according to the present invention, the temperature of the room to be air-conditioned can be reduced by using a small amount of energy, and the life of the equipment installed in the room to be air-conditioned can be prevented from being shortened. In addition, the above effects can reduce the economic burden on the user. In addition, the installation area of the device can be reduced, and the system and control can be simplified. Further, by spraying the cooling water to the condenser, the cooling performance can be further improved.

Further, according to the present invention, in which the cooling water is cooled by a water cooler and blown to the condenser, the cooling performance can be further improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a cooling system according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a cooling system according to another embodiment of the present invention.

FIG. 3 is a schematic diagram of a cooling system according to still another embodiment of the present invention.

[Explanation of symbols]

 1, 1a, 1b ... Cooling system 2 ... Air conditioner 3 ... Condenser 4 ... Cooling tower 4a ... Water cooler 11 ... Steam pipe 12 ... Liquid pipe 21 ... Heat exchanger 60 ... Outside air sensor 62 ... Refrigerant temperature sensor 64 ... Control means 66 ... Pressure sensor

Claims (6)

[Claims] 1. One or more air conditioners having at least a heat exchanger; a single condenser installed higher than the air conditioner; a refrigerant outlet of the air conditioner and a refrigerant inlet of the condenser And a liquid pipe connecting a refrigerant inlet of the air conditioner and a refrigerant outlet of the condenser; and a closed circuit formed by the air conditioner, the steam pipe, the condenser and the liquid pipe. A cooling system comprising: a naturally circulating refrigerant; and cooling the condenser by outside air. 2. The condenser according to claim 1, further comprising a fan for forcibly supplying outside air to the condenser heat exchange unit, and a cooling water circulation mechanism for supplying cooling water to the condenser heat exchange unit. The cooling system according to claim 1, wherein: 3. A cooling tower for lowering the temperature of the cooling water is connected to the cooling water circulating mechanism of the condenser, and the cooling tower blows air to a cooling tower heat exchange section through which the cooling water circulates. The cooling system according to claim 2, wherein the temperature of the cooling water is reduced by: 4. A chiller for lowering the temperature of the cooling water is connected to the cooling water circulation mechanism of the condenser, and the chiller forcibly lowers the temperature of the cooling water using a refrigeration cycle. The cooling system according to claim 2, wherein: 5. An outside air sensor for measuring an outside air temperature, a refrigerant temperature sensor for detecting a temperature of a refrigerant in the cooling system, and a subtraction of an outside air temperature detected by the outside air sensor from a refrigerant temperature detected by the refrigerant temperature sensor. The cooling system according to any one of claims 2 to 4, further comprising control means for operating the cooling water circulation mechanism only when the value obtained is equal to or less than a predetermined value. 6. An outside air sensor for measuring an outside air temperature, a pressure sensor for detecting a pressure of refrigerant vapor in the condenser, and a saturation temperature corresponding to a pressure of the refrigerant vapor detected by the pressure sensor. Control means for operating the cooling water circulation mechanism only when a value obtained by subtracting the outside air temperature detected by the sensor is equal to or less than a predetermined value.
5. The cooling system according to any one of 4.