WO2002004876A1

WO2002004876A1 - A cooling system for active and passive operation

Info

Publication number: WO2002004876A1
Application number: PCT/DK2001/000469
Authority: WO
Inventors: Svend THØGERSEN; Per Pedersen
Original assignee: Dantherm Hms A/S
Priority date: 2000-07-06
Filing date: 2001-07-05
Publication date: 2002-01-17
Also published as: AU2001270483A1; GB2379973B; GB0300730D0; GB2379973A

Abstract

The invention relates to a cooling system having two modes of operation, active and passive operation. The new cooling system differs from the prior art in that the pipe connection (4) is connected with the top of the evaporator (6), and that a liquid separator (9) is arranged between the pipe connections (8) and (10) which connect the bottom of the evaporator (6) with the compressor (1). This ensures that the cooling system may operate free of maintenance, as lubricating oil for lubricating the compressor (1), which is mixed with coolant, accumulates at the bottom of the evaporator (6), from which it may be sucked up and returned to the compressor (1), so that the compressor (1) does not run out of lubricating oil, or that the cooling system must be equipped with other means or deviceds for separating and recycling the lubricating oil to the compressor (1).

Description

A cooling system for active and passive operation

The invention relates to a cooling system consisting of an evaporator and a condenser which are mutually con- nected with a cooling circuit, wherein a throttle means is provided between the evaporator and the condenser, and wherein the cooling system works in active operation with a compressor positioned in the cooling circuit, and wherein the cooling system has means for switching to passive operation, wherein, in passive operation, there is a direct connection between the evaporator and the condenser, said condenser being positioned at a higher level than the evaporator.

In this context, operation in which mechanical energy is fed to the coolant via a pressurizing means, which may be a compressor, is called active operation. Operation solely based on a difference in temperature between the evaporator and the condenser, which results in a natural flow upwards in the form of evaporation of coolant from an evaporator to a condenser and return flow of substantially liquid coolant to the evaporator caused by gravitation, is called passive operation.

Cooling systems having two modes of operation, active and passive operation, are generally known. The advantage of having two modes of operation is that an energy saving can be achieved in periods where the cooling need is not very great, while preserving the possibility of connect- ing a considerably greater cooling power when the need increases . Also a greater reliability of operation is achieved, as the one system can serve as a backup for the other. GB 2 233 080 discloses a cooling system having two integrated modes of operation, active and passive operation. The coolant is passed from the compressor through a directional valve via a pipe connection to a condenser. From there further on to an expansion valve, following which it is passed into an evaporator. The coolant leaves the evaporator at the top through an outlet and is returned to the compressor. In passive operation, two directional valves are switched, thereby disconnecting the compressor and the expansion valve from the cooling circuit. The coolant hereby circulates only through the condenser and the evaporator. The cooling power is extracted by circulating a medium to be cooled through the evaporator, thereby causing heat exchange with the cooled cool- ant. This cooling system has the serious drawback that in active operation it is necessary to have a means for separating the lubricating oil which has been added to the coolant, and which is necessary for lubricating the compressor. Thereby, in addition to the separation means, also means for returning the lubricating oil to the compressor are required, which complicates the cooling system, makes it more expensive and necessitates regular maintenance .

EP 0 641 978 discloses another cooling system having two integrated modes of operation, passive and active operation. The system is the same as GB 2 233 080, but is extended with a heat exchanger circuit. This means that relative to GB 2 233 080 the inlet and the outlet of the evaporator have mounted thereon two heat exchangers, a pipe connection and a circulation pump. The cooling power is extracted in the one heat exchanger, but the unique idea of the technique mainly concerns the second heat exchanger, which operates as a cooling reservoir. The sys- tern is operated with full power in active operation, and when it provides more cooling power than is needed, then the cooling reservoir is charged. When this has been fully charged, the temperature drops on the outlet from the cooling reservoir, which is recorded by a sensor, and the system switches to passive operation. The advantage is stated to be that when switching from active to passive operation, cooling is achieved in the period until the passive operation becomes effective by utilizing the stored capacity in the cooling reservoir. Relative to GB 2 233 080 the cooling system is additionally complicated, just as no solution to the problem of separation and recycling of lubricating oil to the compressor is indicated. If the lubricating oil is not separated right af- ter the compressor and is returned, then the lubricating oil will be transported together with the coolant around in the cooling system, where it will accumulate at various locations, but preferably at the lowest level, so that after a period of time no lubricating oil will ar- rive at the compressor. This means that the compressor has to be drained of and be replenished with the lubricating oil, which requires interruption of operation for maintenance .

Moreover, a cooling system is known from GB 2 314 149 which is also based on GB 2 233 080. It is a cooling system with two integrated modes of operation, active and passive operation. The basic novelty is that a container has been introduced, which serves to accommodate excess coolant in passive operation which would otherwise fill the evaporator and reduce the efficiency. When switching to active operation, where a larger amount of coolant can be used, the container is emptied by conveying heat to it from the condensed coolant by means of a heat exchanger, thereby evaporating the coolant. In addition, heat is also conveyed from an inlet of the evaporator to the heat exchanger, which is likewise in heat-conducting contact with the container. This cooling system has the same drawbacks as GB 2 233 080 and EP 0 641 978, i.e. that the lubricating oil has to be separated right after the compressor and be recycled, which involves interruption of the operation for necessary maintenance.

The object of the invention is to provide a cooling system having an extremely high efficiency and a low consumption of energy, which comprises few components and can operate over a wide temperature range, and which has the additional advantage that the need for maintenance is greatly reduced relative to the existing art.

In connection with independent systems which require cooling, and which may be positioned at isolated and not very easily accessible locations, it is of extremely great importance that the systems are maintenance-free. Such systems may e.g. be unmanned exchanges for mobile telephony, where the electrical equipment is to be cooled to and be kept within a specific temperature range. Here, the combined mode of operation involves an energy-saving possibility of keeping a constant operational temperature on the electrical components, where temperature fluctuations are reduced. The systems may be provided with equipment for remote control, so that e.g. before a repair the temperature may be changed to a pleasant level for the operators who are to carry out the repair.

The new cooling system differs from the prior art in that in active operation the compressor sucks from the bottom of the evaporator via a liquid separator positioned be- tween the evaporator and the compressor, and that the cooling system has means for changing the direction of the flow of coolant through the evaporator when switching between active and passive operation.

This provides a solution to the known problem in cooling systems which operate in active operation, viz. that lubricating oil for lubricating the compressor is mixed with the coolant, which means that the cooling system has to be complicated by incorporation of means and devices to separate and recycle the lubricating oil. Suction from the bottom of the evaporator instead of from the top ensures that the lubricating oil, which accumulates at the bottom of the evaporator, is sucked out of the bottom to- gether with the coolant and up into the compressor in active operation, while in passive operation the lubricating oil substantially also accumulates at the bottom of the evaporator where it is admitted, but substantially remains in this position. In passive operation, the co - pressor does not separate additional oil, so that a need for recycling of oil occurs only in active operation. Thus, the cooling system may work in active as well as passive operation without inexpedient maintenance, which is costly and involves operational losses in connection with temporary interruption.

Coolant may be admitted at the top and be discharged at the bottom of the evaporator in active operation, thereby providing the advantage that lubricating oil accumulated at the bottom of the evaporator is sucked up.

Coolant may be admitted at the bottom and be discharged at the top of the evaporator in passive operation, thereby providing the advantage that the vapours encounter a low resistance to flow.

In active operation, the evaporator may advantageously be supplied with coolant through a special inlet for active operation, wherein the liquid is distributed through distribution ducts and is fed independently to independent sections consisting of pipes or ducts, so that the entire surface of the evaporator is utilized effectively.

Coolant may advantageously be conveyed through an evaporator, which comprises substantially vertical, parallel pipes or ducts, thereby providing an effective evaporation in passive operation as well as a considerable re- duction in the frictional resistance in the evaporator, even though accumulation of the coolant may take place in the evaporator. As a result, the cooling system operates extremely effectively, both when great cooling power is needed and when the need is smaller, and in a temperature range from relatively low to high temperature of the medium which supplies heat to the external surface of the evaporator.

The cooling system may include an evaporator which is di- vided into a plurality of sections in active operation, so that the flow of coolant and lubricating oil through the evaporator is distributed in the sections, and the evaporation can be increased.

When in active operation the condenser is supplied with coolant through an inlet for active operation, wherein the liquid is distributed through distribution ducts and is fed independently to independent sections consisting of pipes or ducts, an advantageous utilization of the entire surface of the condenser is achieved.

When in passive operation the condenser is supplied with coolant through an inlet for passive operation at the higher end of the condenser, it is ensured that the flow resistance in the condenser may be made specially low.

The cooling system may incorporate a shut-off valve be- tween the evaporator and the compressor, which may be open in active operation, so that drainage of coolant through this way, which would otherwise reduce the efficiency in passive operation, may be prevented.

The cooling system may have a design where the outlet of the condenser communicates with at least one throttle means, which is connected with the evaporator, and which is used in active operation, thereby producing a reduction in the temperature of the coolant at a pressure drop before the coolant is admitted into the evaporator.

The cooling system may incorporate a shut-off valve between the outlet of the condenser and the evaporator, so that drainage of coolant through this way, which would otherwise reduce the efficiency in active operation, may be prevented.

The cooling system may incorporate a shut-off valve between the evaporator and the inlet of the condenser, so that drainage of coolant through this way, which would otherwise reduce the efficiency in active operation, may be prevented. When a container is arranged below the condenser, said container being connected at its inlet with the condenser by a pipe connection and being connected at its outlet with a throttle means by another pipe connection and with a shut-off valve by a further pipe connection, it is ensured that a larger amount of coolant may be used in passive operation than in active operation.

When the volume of the container is substantially just as great as the volume of the evaporator or greater, it is ensured that the evaporator may be filled completely when switching from active operation to passive operation.

In active operation the cooling system may advantageously be used at outdoor temperatures in the range above 20 degrees, e.g. in day or summer operation, as the efficiency may be particularly high in this range.

In passive operation the cooling system may advan- tageously be used at outdoor temperatures in the range below 20 degrees, e.g. in night or winter operation, as the efficiency may be particularly high in this range.

In passive operation the cooling system may advan- tageously be used at outdoor temperatures in the range above 20 degrees when the cooling need is smaller, e.g. at reduced energy dissipation in the system, since this results in an energy saving.

In active operation the cooling system may advantageously be used at outdoor temperatures up to 60 degrees, as the efficiency begins to diminish above this range, which, however, is determined by the type of coolant which is used. List of figures

The invention will be described below with reference to Figs. 1 - 7.

Fig. 1 shows a possible embodiment of the cooling system.

Fig. 2 shows a possible embodiment of the active cir- cuit of the cooling system.

Fig. 3 shows a possible embodiment of the passive circuit of the cooling system.

Fig. 4 shows a possible embodiment of a condenser.

Fig. 5 shows a possible embodiment of an evaporator. - Fig. 6 shows a preferred embodiment of the cooling system.

Fig. 7 shows a preferred embodiment of a condenser.

Fig. 1 is a schematic illustration of a possible embodi- ment of the cooling system. A compressor 1 is connected with the top of a condenser 3 by a pipe connection 2. The bottom of the condenser is connected with the top of an evaporator 6 by a pipe connection 4 , which accommodates a throttle means 5 and a dry filter 15. The bottom of the evaporator 6 is connected with a liquid separator 9 by a pipe connection 8, which accommodates a shut-off valve 7. The liquid separator 9 is connected with the compressor 1 by the pipe connection 10. The top of the evaporator 6 is connected with the top of the condenser 3 by a pipe con- nection 11, which accommodates a shut-off valve 12. The bottom of the condenser 3 is connected with the bottom of the evaporator 6 by a pipe connection 14, which accommodates a shut-off valve 13. Active operation takes place in that a mixture of coolant and lubricating oil for lubricating the compressor is pressurized in the compressor 1 and is conveyed in the pipe connection 2 to a condenser 3 in which the mixture is cooled and condensed. The shut-off valves 12 and 13 are closed, while the shut-off valve 7 is open. The condensed coolant is conveyed from the condenser 3 through a dry filter 15 to the throttle means 5 where it is subjected to a pressure drop. The temperature of the coolant drops hereby, and the coolant is conveyed into the top of the evaporator 6. The coolant with the lubricating oil is sucked out of the bottom of the evaporator 6 and is conveyed in the pipe connection 8 to the liquid separator 9, which ensures that only coolant in vapour phase and oil are conveyed further on in the pipe connection 10 back to the compressor.

In passive operation, the shut-off valves 12 and 13 are open, while the shut-off valve 7 is closed. At the same time the inactive compressor 1 serves as a barrier on the pipe connection 2, and the throttle means 5 serves as a barrier on the pipe connection 4. The coolant with the lubricating oil can hereby evaporate and rise from the evaporator upwards via the pipe connection 11 to the con- denser 3, where the coolant with the lubricating oil condenses and flows downwards and back to the bottom of the evaporator 6 through the pipe connection 14. Passive operation may advantageously be used when the temperature of the medium supplying heat to the external surface of the evaporator is higher than the temperature of the medium which cools the external surface of the condenser, i.e. normally the outdoor temperature. The cooling system may advantageously be equipped with a dry filter 15 for separation of harmful water vapour. Generally, the passive circuit of the cooling system must be configured so that the flow resistance is suitably low. The active circuit, on the other hand, may be configured traditionally. Therefore, wherever possible, the shut-off valves 12 and 13 should be of a type which causes the smallest possible pressure drop. This may e.g. be ball valves which are switched by actuators of a hy- draulic, pneumatic or electrical type. Switching of the shut-off valves 12 and 13 may be activated in terms of control at start and stop, respectively, of the compressor 1.

Fig. 2 shows the cooling system of fig. 1, but with the passive part of the cooling system omitted so that the compressor 1 communicates through a pipe connection 2 with a condenser 3, from which a pipe connection 4 communicates through a drying filter 15 with a throttle means 5, which communicates with an evaporator 6. From the outlet of the evaporator at the bottom there is a connection through a shut-off valve 7 and through a pipe 8 to a liquid separator 9, from which a pipe connection 10 provides a connection to the compressor 1.

The compressor 1 compresses coolant which is sucked in from the pipe connection 10, and supplies this coolant at a higher pressure and a higher temperature to the pipe connection 2, from where it is conveyed to the condenser 3. Cooling of the coolant will take place in this, so that condensing occurs. At the outlet of the condenser and in the pipe connection 4, the coolant will be present in liquid form under a high pressure. The liquid coolant is conveyed through a drying filter 15 to a throttle means 5, which may e.g. be a traditional thermostatic expansion valve. The liquid coolant is fed from there to the evaporator 6. The coolant is converted in the evaporator, under absorption of heat, from liquid form into gas form, which is sucked by the compressor at the bottom of the evaporator through the shut-off valve 7 and through the liquid separator 9 to the inlet of the compressor.

Fig. 3 shows the cooling system of fig. 1 in passive operation. At its outlet the condenser 3 communicates through the pipe connection 14 and through an open shut- off valve 13 with the inlet of the evaporator 6, the admission being now at the bottom. From the outlet of the evaporator 6 at the top, there is a connection to the inlet of the condenser 3 through a pipe connection 11 and an open shut-off valve 12.

Provided that there is a higher temperature around the evaporator 6 than around the condenser 3, evaporation of coolant can be achieved in the evaporator 6, from which the coolant is conveyed through the pipe connection 11 to the condenser 3 , where the lower temperature causes condensation of the gaseous coolant . The liquid coolant in the condenser 3 has a greater density than the gas, and liquid coolant will therefore run through the pipe connection 14 to the evaporator 6, which may be flooded by liquid coolant to a certain extent, from which it can evaporate again. In the passive operation, heat is con- veyed away from the evaporator 6 to the condenser 3, without a coolant flow having to be driven by anything but the prevailing temperature difference. Fig. 4 shows a possible embodiment of the condenser 3 with an inlet 16 and an outlet 17, said condenser consisting of a plurality of parallel pipes 18 which are mutually connected by distribution ducts 19 at the inlet 16 and the outlet 17, respectively.

The use of the vertical ducts 18 ensures that the condenser has a minimum flow resistance, which is necessary to achieve a high efficiency in passive operation.

Fig. 5 correspondingly shows an evaporator with an inlet for active operation 20 and an inlet for passive operation 21, an outlet for passive operation 22 and an outlet for active operation 23. The evaporator consists of a plurality of vertically positioned pipes or ducts 24 as well as distribution ducts 25.

In active operation the evaporator 6 is supplied with coolant through the inlet for active operation 20, where the liquid is distributed through distribution channels 25, and is connected with the individual pipes or ducts 24 e.g. via a plurality of pipes having a considerably smaller diameter than the inlet 20. This results in increased flow resistance, which ensures that liquid is supplied in all the vertical ducts. Evaporation of the supplied liquid takes place in the ducts 24, and then, in operation, it will be possible to suck evaporated coolant at the outlet 2 further toward a compressor 1. In passive operation, the evaporator is used conversely, as a spe- cial outlet for passive operation 22 communicates with the condensing unit 3, while an inlet for passive operation 21 likewise communicates with the condensing unit, but this time with its outlet. That is, in passive operation the evaporator is supplied with liquid coolant at the bottom, following which evaporation takes place so that coolant in gas form passes through the outlet 22 to the condensing unit 3. For the passive operation to take place optimally, it is necessary that the entire cooling system is constructed with minimum flow restrictions in all components. When switching between passive and active operation, however, it will have to be taken into special consideration that the evaporator 6 may be flooded at this time, and the compressor 1, which sucks from the bottom of the evaporator, risks sucking in liquid. Therefore, in a cooling system of this type, it is strictly necessary to use a liquid separator 9 between the evaporator 6 and the compressor 1. A liquid separator is a device that allows medium in vapour and mist form to pass, but retains medium in liquid form, so that the compressor is not damaged. However, suction from the bottom of the evaporator ensures that oil, which has accumulated at the bottom of the evaporator 6, is hereby conveyed through the liquid separator 9 to the compressor 1, together with the coolant flow.

Fig. 6 is a schematic illustration of a preferred embodiment of the cooling system. The cooling system is substantially identical with the one shown in fig. 1, except that the compressor 1 is connected with an inlet on the condenser 3 separate from the pipe connection 11, and that the outlet of the condenser 3 is connected with a container 30 on the inlet side by the pipe connection 32, and that the outlet of the container 30 is connected with the throttle means 5 as well as the dry filter 15 via the pipe connection 4 and with the shut-off valve 13 via the pipe connection 14. The stated changes relative to fig. 1 mean that it is possible to use a condenser type as stated in the following description of fig. 7. Moreover, it is ensured that in active operation the container 30 may contain excess coolant, if any. Frequently, a considerably larger amount of coolant will be needed in passive operation than in active operation. When the system then switches from passive to active operation, any excess coolant will be collected in the container 30, as the shut-off valve 13 is closed and the throttle means 5 is controlled relative to the amount of coolant in the evaporator 6. This avoids overfilling of the evaporator 6. When the system switches back to passive operation from active operation, the container 30 is emptied as the shut-off valve 13 opens.

Fig. 7 shows a preferred embodiment of the condenser 3. This comprises an inlet for active operation 34 and an inlet for passive operation 16 as well as an outlet 17 for both active and passive operation. The condenser 3 consists of a plurality of vertically positioned pipes or ducts 18 as well as distribution ducts 19.

In active operation the condenser 3 is supplied with coolant through the inlet for active operation 34, where the liquid is distributed to the individual pipes or ducts 18 e.g. via a plurality of pipes having a consid- erably smaller diameter than the inlet 34. This results in an increased flow resistance, which ensures that liquid is fed to all the vertically extending ducts 18. In passive operation the inlet 16 is used where the flow resistance is considerably lower.

The cooling system is preferably used with coolants which comprise one or more media suitable for transporting lubricating oil back to a compressor. As a result, the cooling system can be kept in operation without maintenance .

The compressor of the cooling system may advantageously be of the hermetic type so that the cooling system may be constructed with particularly great tightness, but also semi-hermetic or other suitable types may be used.

A cooling system as illustrated in the drawings and de- scribed in the description above lends itself particularly to the cooling of electrical equipment, including mobile transmitter stations, as the electronic units operate at an ambient temperature of about 40 degrees Celsius, which exceeds the outdoor temperature in most cases, thereby allowing passive operation to be used to a great extent . This results in an annual saving of the order of 65% - 75% of the electrical power which would otherwise have to be used for cooling e.g. a mobile transmitter station. Passive operation may be used for a great part of the day, as e.g. mobile transmitter stations only have a max. power dissipation for short periods of time when there is great mobile communication via the individual transmitter. During periods with less traffic via the transmitter station and with a simultaneous low outdoor temperature e.g. at night, the passive operation will be fully sufficient for cooling the mobile transmitter station, just as in the winter period active cooling will probably not be needed at all. If the outdoor temperature increases, e.g. on a hot summer day, with a simultaneous maximum load on a mobile network, the temperature in the mobile transmitter station will increase, however, and the passive operation will not have sufficient capacity for cooling, and therefore the system switches to active operation. In situations with e.g. failure of the supply mains so that a transmitter station e.g. has to be powered by batteries, the passive operation of the cooling system will start automatically, so that cooling will be applied to the electronic system, perhaps to a limited extent, but in an emergency situation the transmitter system will also disconnect parts of the power-generating transmitter systems, so that cooling requirement and power dissipa- tion correspond to each other to a certain extent, the passive operation being intensified and getting more effective in step with the increase in the temperature internally in a transmitter station. This means that in case of power failure the transmitter will be able to work relatively undisturbed during the entire period where the battery capacity can cover the electrical supply, without any switching-off taking place because of a high temperature inside the transmitter station.

Claims

Patent Claims

1. A cooling system for active and passive operation, comprising a compressor (1) whose outlet is connected with a condenser (3) via a pipe connection (2) , said condenser being connected with the inlet to an evaporator (6) via a pipe connection (4) in which a throttle means

(5) is arranged, the outlet of said evaporator being connected with the inlet of the compressor (1) via pipe con- nections (8 and 10) , as well as a further pipe connection (14) with a shut-off valve (13) which connects the condenser (3) with the evaporator (6) bypassing the throttle means (5) , and a pipe connection (11) which, without any further incorporated means than a shut-off valve (12) , connects the evaporator (6) with the inlet to the condenser (3) , said condenser being arranged at a higher level than the evaporator (6) , characterized in that the pipe connection (4) is connected with the top of the evaporator (6) , and that a liquid separator (9) is ar- ranged between the pipe connections (8 and 10) which connect the bottom of the evaporator (6) with the compressor (1).

2. A cooling system according to claim 1, characterized in that the coolant and the lubricating oil are admitted at the top (20) and discharged from the bottom (23) of the evaporator (6) in active operation.

3. A cooling system according to claim 1 or 2, charac- terized in that the coolant is admitted at the bottom

(21) and discharged from the top (22) of the evaporator

(6) in passive operation.

4. A cooling system according to one or more of claims 1 to 3, characterized in that the coolant is conveyed through the evaporator (6) in substantially vertical parallel pipes or ducts (24) .

5. A cooling system according to one or more of claims 1-4, characterized in that in active operation the evaporator (6) is supplied with coolant through an inlet for active operation (20) , wherein the liquid is distributed through distribution ducts (25) and is fed independently to independent sections consisting of pipes or ducts (24) .

6. A cooling system according to one or more of claims 1-5, characterized in that the coolant is conveyed through the condenser (3) in substantially vertical parallel pipes or ducts (18) .

7. A cooling system according to one or more of claims 1-6, characterized in that in active operation the condenser (3) is supplied with coolant through an inlet for active operation (34) , wherein the liquid is distributed through distribution ducts (19) and is fed independently to independent sections consisting of pipes or ducts (18) .

8. A cooling system according to one or more of claims 1-7, characterized in that in passive operation the condenser (3) is supplied with coolant through an inlet for passive operation (16) at the higher end of the condenser (3).

9. A cooling system according to one or more of claims 1-8, characterized in that a shut-off valve (7) , which is closed in passive operation, is arranged between the evaporator (6) and the compressor (1) .

10. A cooling system according to one or more of claims 1-9, characterized in that the outlet of the condenser (3) communicates with at least one throttle means (5) connected with the evaporator (6) , said throttle means being used in active operation.

11. A cooling system according to one or more of claims 1-10, characterized in that a shut-off valve (13) is arranged between the outlet of the condenser (3) and the evaporator (6) , said shut-off valve being closed in active operation and open in passive operation.

12. A cooling system according to one or more of claims 1-11, characterized in that a shut-off valve (12) is arranged between the evaporator (6) and the inlet of the condenser (3) , said shut-off valve being closed in active operation and open in passive operation.

13. A cooling system according to one or more of claims 1-12, characterized in that a container (30) is arranged below the condenser (3) , said container being connected at its inlet with the condenser (3) by a pipe connection (12) and being connected at its outlet with the throttle means (5) by the pipe connection (4) and with the shut- off valve (13) by the pipe connection (14) .

14. A cooling system according to claim 13, characterized in that the volume of the container (30) is substantially just as great as the volume of the evaporator (6) or greater.

15. A cooling system according to one or more of claims 1-14, characterized in that active operation is preferably used at outdoor temperatures in the range above 20 degrees .

16. A cooling system according to one or more of claims 1-15, characterized in that passive operation is preferably used at outdoor temperatures in the range below 20 degrees .

17. A cooling system according to one or more of claims 1-16, characterized in that passive operation at a low cooling need is preferably used at outdoor temperatures in the range above 20 degrees.

18. A cooling system according to one or more of claims 1-17, characterized in that active operation is preferably used at outdoor temperatures in the range up to 60 degrees .