AT17395U1 - DEVICE AND METHOD FOR CONTINUOUS COOLING - Google Patents

Abstract

A once-through cooling device is described, comprising: a container that can be filled with a first liquid; a first conduit arranged in the container and through which a second liquid can pass; a cooling device configured to cool the first liquid in the container; and a controller which is designed to activate and deactivate the cooling device depending on a signal which depends on a volume or a filling level of the first liquid in the container.

Description

description

DEVICE AND METHOD FOR CONTINUOUS COOLING

TECHNICAL AREA

The present description relates to a device for continuous cooling and a corresponding method for continuous cooling.

BACKGROUND

[0002] Two different principles are mainly known for continuous cooling of beverages in conventional vending machines: dry cooling and wet cooling. With dry cooling, cold air flows in a flow spiral through which the liquid to be cooled flows in a cooling block. Dry cooling is particularly fast and compact, but cannot reach low temperatures. With wet cooling, an ice bank is formed in a water bath, whereby the liquid to be cooled, which flows through a flow spiral located in the water bath, can be cooled. With wet cooling, temperatures around the freezing point of water (0° Celsius) can be reached, which is important for carbonizing the liquid to be cooled. However, wet cooling is much more complicated in use than dry cooling.

An important aspect of wet cooling is that the formation of ice must be precisely controlled to prevent the liquid to be cooled (e.g. water, juice or beer, etc.) from freezing, which can negatively affect the quality of the beverage in particular . This is usually achieved by maintaining a certain distance between the ice bank and the flow-through spiral, which is typically achieved by a large container design, and by closely monitoring ice formation. Ice formation in the container is typically monitored using capacitive sensors. Although capacitive sensors are very precise, they are also expensive. In addition, their accuracy is limited in the case of uneven ice formation, for example with ice-water mixtures.

The inventors have set themselves the task of developing a once-through cooling device which can combine the advantages of dry and wet cooling, and in particular a wet cooling device which is compact and inexpensive and has simple control.

SUMMARY

The above objects are achieved by a once-through cooling device according to claim 1 and by a once-through cooling method according to claim 17 . Various embodiments and further developments are the subject of the dependent claims.

A device for once-through cooling is described, comprising: a container that can be filled with a first liquid; a first conduit arranged in the container and through which a second liquid can pass; a cooling device configured to cool the first liquid in the container; and a controller which is designed to activate and deactivate the cooling device depending on a signal which depends on a volume or a filling level of the first liquid in the container.

According to a further exemplary embodiment, a method for once-through cooling is described, which comprises the following steps: cooling a first liquid located in a container by means of a cooling device, whereby a second liquid which runs through a first line located in the container is cooled; and activating and deactivating the cooling device depending on a signal that depends on a volume or a level of the first liquid in the container.

BRIEF DESCRIPTION OF ILLUSTRATIONS

The invention is explained in more detail below with reference to the examples shown in the figures. The illustrations are not necessarily to scale, and the invention is not limited to only the aspects illustrated. Instead, value is placed on presenting the principles on which the invention is based. About the pictures:

Figure 1 shows a perspective view of a device for continuous cooling according to an embodiment.

Figure 2 shows a cross-sectional view of the device according to the embodiment of Fig. 1.

[0011] FIG. 3 shows a flow chart of a method for continuous cooling according to an exemplary embodiment.

DETAILED DESCRIPTION

Two different principles are mainly known for continuous cooling of the drinks in conventional vending machines: dry cooling and wet cooling. In the case of dry cooling, the liquid to be cooled flows through a pipe which is subjected to a flow of cold air. The cold air transports the heat away from the liquid. Typically, the liquid to be cooled is stored in a cooling block, which is made of aluminum, for example, and in which the cool air flows. The dry cooling has the particular advantage that it can be put into operation particularly quickly. It typically takes 10 to 15 minutes for dry cooling to cool 250 mL of a liquid from room temperature to around 5°C. In addition, no complex maintenance is necessary and the dry cooling can be used without any problems in non-stationary environments such as ships or trains. Dry cooling is also particularly practical because of the smaller design of the cooling block. However, such an aluminum cooling block is expensive to manufacture. It is also felt to be disadvantageous that the aluminum cooling block has a very sluggish thermal behavior. In addition, the transfer of cold from aluminum to the continuous spiral is not optimal due to the formation of air pockets. In addition, it is not possible to reach temperatures around the freezing point of water. This means that carbon dioxide used to carbonate the beverage is not sufficiently cooled. Dry cooling is therefore not suitable for carbonated drinks.

In wet cooling, on the other hand, a water bath is used, in which the flow spiral, through which the liquid to be cooled flows, is arranged. A cooling device is also provided which causes ice to form in the water bath, thereby reducing the temperature of the water bath and the liquid in the flow-through spiral. A stirrer is typically used to achieve an even temperature distribution in the water bath. Compared to dry cooling, such wet cooling is much more economical to produce, since no aluminum casting is necessary and the container for the water bath can be made of plastic, for example. In addition, low temperatures around the freezing point of water (i.e. 0° Celsius) can be reached without difficulty, which is advantageous for the carbonation of the chilled beverage. Due to the direct contact between the water bath and the beverage flow spiral, optimal cold transfer can also be achieved. The wet cooling can be delivered without a filled water bath and is therefore easy to transport. The cold can also be stored by forming an ice bank, which is typically formed as a layer of ice with a thickness of 2 to 3 cm on the inner walls of the container, so that wet cooling can be relatively energy-saving. However, wet cooling is much slower than dry cooling, typically taking 40 to 50 minutes to bring the water bath temperature to 5°C. Since the water can leak from the water bath, operation in non-stationary environments is also more complex.

An important aspect of wet cooling is that both the level of the water bath

ice formation must also be precisely controlled, which entails a corresponding control and sensor system, which makes the operation of wet cooling more complex. In particular, with wet cooling, care must be taken to ensure that the liquid to be cooled (e.g. drinking water, juice or beer, etc.) does not freeze, which could negatively affect the quality of the beverage. Therefore, a certain spatial distance between the ice bank and the continuous spiral must be maintained, which is typically achieved by a relatively large design of the container. Ice formation is usually measured and monitored using capacitive sensors. Since ice and water have different dielectric constants, the ice-water ratio in the water bath can be measured using the measured dielectric constant (or the electrical capacitances that depend on it). Although this method is particularly useful when ice formation is uniform, it is difficult to accurately detect ice-water mixtures. In any case, freezing of the water should be avoided.

There are shown in the figures, a device and a method for continuous cooling, which at least wisely overcome the usual disadvantages of wet cooling or at least improve the situation.

Figures 1 and 2 shows a perspective view (Figure 1) and a cross-sectional view (Figure 2) of a device 100 for continuous cooling according to an embodiment.

The device 100 comprises a container 1, a first line 2 through which a liquid to be cooled (usually a beverage) flows, and a second line 3 through which a refrigerant can flow. According to the exemplary embodiments described here, the container is filled with water for the cooling operation, so that a water bath is formed in which the first line 2 and the second line 3 are located. Cooling liquids other than water are conceivable, with water remaining a common and inexpensive option. The first line 2 and the second line 3 are arranged in the container 1 and in the water bath, respectively. In the exemplary embodiment shown, the first line 2 is in the form of a spiral line and the second line 3 is in the form of a cooling coil (cooling spiral), the cooling coil 3 enclosing the first line 2 . However, other arrangements of the lines 2, 3 are conceivable.

The liquid to be cooled can be a beverage such as water, juice, beer or the like. Refrigerant is usually understood to mean a fluid that is used for heat transfer in a refrigeration system, and which absorbs heat at low temperature and low pressure and gives off heat at higher temperature and higher pressure. Usually, these heat transfers are associated with changes in the state of the fluid.

As can be seen from FIG. 2, the ends of the cooling coil 3 are connected to a compressor 20 arranged outside of the container, so that the compressor 20 and the cooling coil 3 form a compression refrigerating machine. A compression refrigeration machine is a cooling device in which a refrigerant is moved in a closed circuit. The refrigerant is compressed by the compressor 20 and heats up in the process. The refrigerant then releases its heat and flows through a throttle (not shown), resulting in a pressure drop. The refrigerant cooled in this way flows through the second line 3 inside the container 1 and removes heat from the water bath, as a result of which the water bath is cooled. The refrigerant then flows back to the compressor 20. By cooling the water in the tank 1 an ice bank can form around the second pipe 3 and in particular a layer of ice with a thickness of for example 2 to 3 cm can form on the walls 40 of the tank. The chilled water bath then cools the liquid in line 2 to be cooled.

To monitor the formation of ice, the device comprises 100 sensors 6a and 6b, which are arranged on the container 1. In conventional flow-through coolers, capacitive sensors are used for this purpose, which measure a dielectric constant of the liquid in the container (i.e. the water bath) and can derive a ratio between ice and water in the water bath from this. In contrast, according to this embodiment, the sensors 6a, 6b as

Formed level sensors, which are designed to detect the level in the container 1 or to measure. Namely, when ice is formed in the container 1, the level in the container 1 increases accordingly, since ice has more volume than liquid water. The sensors 6a, 6b can be simple floats, for example, which can detect when a predetermined filling level is exceeded. Other types of level sensors can also be used. For example, optical sensors, ultrasonic sensors or radar sensors can also measure fill levels.

The sensors 6a, 6b can monitor a predetermined threshold and send a corresponding signal when the level reaches this threshold. In the embodiment shown, the threshold is represented by a maximum ice-water line 8 . The threshold can be chosen so that it corresponds to the case in which the ice layer formed becomes so thick that it just touches the liquid line 2 . According to the embodiment shown, the sensors 6a, 6b are arranged diagonally opposite one another. By using two sensors 6a, 6b, it is possible to compensate for fluctuations in the waterline when the device 100 is not stationary (e.g. if the water sloshes back and forth due to movement of the device). However, it is also possible to use a single filling level sensor or a large number of filling level sensors which are intended to monitor different levels, for example.

A fill level measurement is not useful in conventional wet cooling systems, since these generally have a relatively large design in which the container is comparatively wide, i.e. with a large base area. This is to ensure that a sufficient distance is maintained between the ice bank and the continuous spiral in order to prevent the liquid to be cooled from freezing. Because of the relatively large base area of the container, however, the variation in the fill level is too small to be able to be detected with sufficient accuracy using conventional fill level sensors. In contrast, according to the embodiment of FIGS. 1 and 2, a simple level measurement is possible because the container 1 has a special shape.

The container 1 can be essentially rectangular or cylindrical and has a base 30 and side walls 40 (see FIG. 2). Compared to the tanks of conventional wet coolers, the base area 30 is relatively small and the walls 40 are relatively high. In particular, a height of the walls 40 is greater than a largest dimension (e.g. the diameter for cylindrical containers) of the base 30.

According to the embodiment shown in FIGS. 1 and 2, the base 30 is essentially square, with a height H of the container 1 being larger, in particular approximately more than 2 times larger than the side length L of the base of the container 1. However, other ratios between the length and the height of the container are also possible, as long as the height is greater than the length of the container. For example, the height of the walls 40 can be more than 1.5 times greater, more than 2 times greater, or more than 3 times greater than the largest dimension of the base area 30 . This means, on the one hand, that the device 100 is designed to be particularly compact, which results in a shorter time until the cooling system is ready for operation of approximately 30 minutes after the device 100 is switched on. On the other hand, changing the size of tank 1 (from "wide and low" to "narrow and high") also means that the ice bank that forms during operation leads to a significant change in the water level, which can be easily and accurately monitored with a simple level sensor is. It is thus possible to use level sensors as monitoring sensors 6a, 6b. Expensive capacitive sensors can then be dispensed with. The cylindrical or prismatic shape of the container 1 with a relatively small base area 30 and relatively high walls 40 makes it possible to easily and relatively precisely control and monitor the fill level and thus the extent of the ice bank. The container 1 can be made of plastic, so that the device 100 is particularly inexpensive and easy to manufacture.

In the example shown, the device 100 comprises a cover 11 which can seal the container 1 (and the water bath located therein) tightly. Thus, an operation

possible in non-stationary installation. The cover can be made of metal, with the outlets of the lines 2, 3 being able to pass through the cover 11.

The device further includes a controller 50 which is designed in particular to control the compressor 20 and thus a cooling device formed by the compressor 20 and the cooling coil 3 . According to the exemplary embodiments described here, the controller 50 can activate or deactivate the cooling device depending on a signal from one or more level sensors (e.g. sensors 6a, 6b), which represents the volume or the level of the water-ice mixture in the container 1. In particular, the controller 50 can switch the compressor 20 on or off depending on the signals from the level sensors 6a, 6b.

As soon as the level in the container 1 exceeds the predefined ice-water line 8, this excess is detected by the level sensors 6a, 6b and a corresponding signal is transmitted to the controller 50. The controller 50 can then switch off the compressor 20 so that ice formation is stopped. It is thus possible to prevent the liquid to be cooled from freezing in the first line 2 (flow spiral). Since the controller 50 controls the compressor 20 depending on the volume or filling level of the ice-water mixture in the container 1, a layer thickness of the ice bank can also be influenced indirectly.

The device 100 can also have a carbonator tank 4 containing carbon dioxide. Carbon dioxide can thus be dissolved in the liquid to be cooled in a manner known per se, in order to obtain sparkling water or the like at the outlet of the device 100, for example. According to the embodiment shown, the carbonator tank 4 is arranged in the container 1, with the first line 2 enclosing the carbonator tank 4 in the example shown, or being wound around the carbonator tank 4 and touching it. The carbonator tank 4 is cylindrical. The carbonator tank 4 is also cooled by the water bath, with low temperatures around the water freezing point being desired.

The filling of the container 1 with water takes place via an inlet pipe 12 which opens into the container 1 at the upper end thereof. In order to enable automatic filling, the throughput of the water flowing into the container 1 can be controlled. In the example shown, a valve 121, which can for example be an electromagnetic valve, is arranged on the inlet pipe 12 and which can regulate the water flow rate. The valve 121 is controlled by the controller 50 as a function of the water level in the container 1. For this purpose, at least one filling level sensor 5a, 5b is arranged on the container 1, which is suitable for monitoring the filling level in the container 1 and in particular whether it falls below or exceeds the nominal water line 7. As soon as the waterline 7 is reached, the level sensor 5a sends a corresponding signal to the controller 50. The controller 50 then sends a signal to the valve 121 so that the valve 121 closes and no more water can flow into the container 1. According to the embodiment, two level sensors 5a, 5b are arranged on the container 1, which monitor the water line 7. The sensors 5a, 5b are arranged diagonally opposite one another in order to enable compensation for fluctuations in the water line when the device 100 is not fixed in one place. Depending on the type of fill level sensor used, a single sensor can also be sufficient. The latter is possible, for example, if the level sensor is designed as a radar sensor or an optical sensor, which can thus monitor multiple thresholds. If simple floats are used as level sensors, several sensors can be useful. If the liquid to be cooled is drinking water, the water bath can also be filled automatically and monitored via the same drinking water connection as the drinking water to be cooled, so that no additional connection is necessary.

In some exemplary embodiments, the water in the container 1 is constantly moved after the filling of the container 1 during operation in order to achieve a uniform temperature distribution in the container 1 . The water is introduced into the container 1 via the inlet pipe 12 and sucked out of the container 1 via an outlet pipe 11 . The inlet tube 12 terminates at an upper end of the container 1 and the outlet tube 11 terminates at a lower end of the container 1,

i.e. near the base 30. The water circulation in the tank 1 is controlled by a circulation pump 9 arranged outside the tank 1, which is coupled to the inlet pipe 12 and the outlet pipe 11. The water circulation enables a homogeneous temperature distribution in the water bath. Compared to conventional agitators, which are arranged in the container 1, an external circulation pump has the advantage that an additional cooling possibility for the water in the pipes 11, 12 is possible outside the container 1, for example in the form of a with the pipes 11, 12 associated cooling box 10. This additional accompanying cooling, the water can be cooled before being introduced into the container 1, which can facilitate the work of the compressor 20. In addition, the container 1 can remain compact since no agitator is used in the container. The circulation pump 9 can be easily controlled by the controller 50.

At least one temperature sensor for measuring the water temperature is used to control the circulation pump 9 . The controller 50 can then control the circulation pump 9 depending on a signal from the temperature sensor. In one exemplary embodiment, two temperature sensors 111, 121 are provided, with the temperature sensor 121 being arranged at one end of the inlet pipe 12 at the upper end of the container 1 and the temperature sensor 111 being arranged at one end of the outlet pipe 11 at the lower end of the tank 1. The controller can control the circulation pump 9 depending on a signal from the first temperature sensor 121 and a signal from the second temperature sensor 111 . If, for example, a temperature difference between a temperature measured at the top of the container 1 and a temperature measured at the bottom of the container 1 is too high, ie a predetermined threshold is exceeded, the speed of the circulation pump 9 is increased by the controller 50 to the Reduce temperature difference and thus achieve a better temperature distribution in the container 1.

In one embodiment, a delivery temperature of the liquid to be cooled, e.g., drinking water, can also be controlled. For this purpose, a further line 14 is provided, through which a liquid flows at a specific temperature, for example uncooled tap water, and which is coupled to the flow-through cooling line 2 in such a way that the liquid in the flow-through cooling line 2 and the liquid in line 14 are mixed will. The mixed drink then flows into an outlet line 15. For example, the flow-through cooling line 2 can contain chilled (possibly concentrated) fruit juice and the further line 14 can contain non-chilled drinking water, so that a mixed drink made of fruit juice and water is dispensed at a temperature that is higher than that of the chilled fruit juice. FIG. 1 shows that the device 100 can also have a valve 16 which is coupled to the outlet 22 of the flow-through cooling line 2 and to the line 14 . The valve 121 is controlled by the controller 50 in such a way that the mixed drink in the outlet line 15 has a desired temperature. For this purpose, a first temperature sensor 21a is arranged at an inlet of the continuous-flow cooling coil 2 and a second temperature sensor 21b is arranged at an outlet of the continuous-flow cooling coil 2, which monitor the temperature of the liquid to be cooled. The valve 121 is controlled depending on the signals from the temperature sensors 21a, 21b. According to the embodiment, the valve 16 is designed as an electromagnetic 3/2-way valve, which lets through either the liquid to be cooled in the flow spiral 2 or the liquid at a predetermined temperature in the line 14 . However, it is also conceivable to use a different number of temperature sensors or a different type of valve.

To monitor the cooling, a further temperature sensor 21 can also be arranged on the housing of the compressor 20, which monitors a temperature of the refrigerant in the compressor 20. If the monitored temperature reaches or exceeds a predetermined threshold, the temperature sensor 21 sends a corresponding signal to the controller 50, which then switches off the compressor 20 automatically. A corresponding error is then reported.

There are a number of possible sources of error in the cooling, which should be monitored. In particular, the controller 50 of the device 100 can be designed to recognize such error sources and to report corresponding errors, which in particular

a shutdown of the compressor 20 or the circulation pump 20 may result. Typical faults are insufficient supply and exhaust air, a loss of refrigerant from the circuit or an overload of the device 100, for example if the water inlet temperature is too high (i.e. above 30°C).

FIG. 3 shows a flow chart of a method for continuous cooling according to one embodiment. In a first step 101, a first liquid located in a container 1, which is typically water, is cooled by means of a cooling device, as a result of which a second liquid, which runs through a first line 2 located in the container 1, is cooled. The cooling device can have a second line 3, which is arranged in the container 1, and a compressor 20, which is coupled to the second line 3 and is adapted to compress a refrigerant located in the second line 3, whereby the first liquid heat is withdrawn. In a second step 102, the cooling device is activated or deactivated depending on a signal that depends on a volume or a fill level of the first liquid in the container 1. For example, the compressor 20 can be turned on and off depending on this signal. In addition, the filling level of the first liquid in the container 1 can be monitored and the compressor 20 switched off when the monitored filling level reaches a predefined threshold. The container 1 can be filled automatically at the beginning of the cooling process. A filling level of the water in the container 1 can be monitored and the container 1 can be filled depending on the monitored filling level of the water. In particular, filling of the container 1 can be stopped when the monitored water level reaches a predetermined threshold. During the actual cooling, a water circulation can be effected in the container 1 in order to achieve an optimal temperature distribution in the container 1.

The device 100 has the particular advantage that rapid and accurate cooling can be effected using only simple and inexpensive sensors for monitoring the formation of ice in the water bath. Due to its small design, the device 100 can also be used particularly quickly.

Claims (19)

Expectations 1. Device for once-through cooling, which comprises: a container (1) which can be filled with a first liquid, a first line (2) which is arranged in the container (1) and through which a second liquid can pass, a cooling device adapted to cool the first liquid in the container (1), and a controller (50) which is designed to activate and deactivate the cooling device depending on a signal which depends on a volume or a filling level of the first liquid in the container (1). 2. The device according to claim 1, wherein the cooling means comprises a second line (3) arranged in the container (1) and a compressor (20) coupled to the second line (3) and adapted to to compress a refrigerant located in the second line (3), as a result of which heat is extracted from the first liquid. 3. The device according to claim 2, wherein the second line (3) is a cooling coil arranged in the container (1). 4. The apparatus according to claim 2 or 3, wherein the first conduit (2) is helical and is located adjacent to the cooling coil. 5. The device according to claim 4, wherein the second conduit (3) encloses the first conduit (2). 6. Apparatus according to any one of the preceding claims, further comprising: a carbonator tank (4) containing carbon dioxide under pressure and arranged in the container (1), the first conduit (2) enclosing the carbonator tank (4). 7. Device according to one of claims 2 to 6, which further comprises: at least one level sensor (6a, 6b) for monitoring the level of the first liquid in the container (1), wherein the controller (50) is further adapted to the compressor (20) turn off when the monitored level reaches a predefined threshold. 8. Device according to one of the preceding claims, wherein the container (1) is essentially cylindrical and has a base (30) and walls (40) extending upwards from the base (30), with a height of the walls (40 ) is larger than a largest dimension of the base (30), preferably more than 1.5 times larger, preferably more than 2 times larger, preferably more than 3 times larger. 9. Device according to one of the preceding claims, which further comprises: a first valve (121) which is designed to regulate an entry of the first liquid into the container (1), the controller (50) being further designed to to control the first valve (121) depending on the filling level of the first liquid in the container (1). 10. The device according to claim 9, which further comprises: _ at least one further level sensor (5a, 5b) for monitoring the level of the first liquid in the container (1), wherein the controller (50) is further designed to switch the first valve (121 ) to close when the level monitored by the further level sensor (5a, 5b) reaches a further predefined threshold. 11. 12. 13. 14 15 16 17 18 Austrian AT 17 395 U1 2022-03-15 Apparatus according to any one of the preceding claims, further comprising: an inlet tube (12) through which the first liquid can pass and be introduced into the container (1), an outlet tube (11) through which the first liquid can pass and be sucked out of the container (1), a circulation pump (9) coupled to the inlet pipe (12) and the outlet pipe (11) and adapted to allow the first liquid to circulate in the container (1). Apparatus according to claim 11, further comprising: at least one temperature sensor, which is designed to measure a temperature of the first liquid, wherein the controller (50) is further designed to control the circulation pump (9) as a function of a signal from the temperature sensor. Device according to one of claims 11 or 12, further comprising: a first temperature sensor (121) arranged on the inlet pipe (12) and adapted to measure a temperature of the first liquid in the inlet pipe (12), and a second temperature sensor (111) arranged on the outlet pipe (11) and adapted to measure a temperature of the first liquid in the outlet pipe (11), wherein the controller (50) is further adapted to activate the circulation pump (9) depending on a signal of the first temperature sensor (121) and by a signal of the second temperature sensor (111). Apparatus according to any one of the preceding claims, further comprising: a third temperature sensor (21a, 21b), which is designed to measure a temperature of the second liquid, a mixing device which is designed to mix the second liquid with a third liquid, wherein the controller (50) is designed to control the mixing device as a function of the temperature of the second liquid. Apparatus according to claim 14, wherein the mixing device comprises a third line (14) through which the third liquid can pass and a second valve (16), the third line (14) being connected via the second valve (16) to an outlet (21) of the first line ( 2) connected, wherein the controller (50) is designed to control the second valve (16) depending on the temperature of the second liquid. Apparatus according to any one of claims 2 to 15, further comprising: a fourth temperature sensor (21) which is arranged on the housing of the compressor (20) and is designed to measure a temperature of the compressor, wherein the controller (50) is adapted to turn off the compressor (20) when the temperature of the compressor (20) reaches a predefined threshold. A method of once-through cooling, comprising the steps of: Cooling (101) of a first liquid in a container (1) by means of a cooling device, whereby a second liquid which runs through a first line (2) in the container (1) is cooled, Activating and deactivating (102) the cooling device depending on a signal which depends on a volume or a filling level of the first liquid in the container (1). A method according to claim 17, wherein the cooling means comprises a second duct (3) arranged in the container (1) and a compressor (20) coupled to the second duct (3) and adapted to be a located in the second duct (3). to compress refrigerant, thereby removing heat from the first liquid, and the method further comprises the following step: Switching the compressor (20) on and off depending on a signal which depends on a volume or a level of the first liquid in the container (1). 19. The method according to claim 18, further comprising the following steps: monitoring the filling level of the first liquid in the container (1), switching off the compressor (20) when the monitored filling level reaches a predefined threshold. 2 sheets of drawings