Technical Field

The present disclosure relates to technology for cooling milk, and in particular a dual cooling system including a chiller that cools down a coolant used for both cooling milk in a heat exchanger and in a tank.

Background

Milk collected at a farm needs to be cooled down fast to avoid bacterial growth. In order to deliver premium milk, the milk has to have a high quality when delivered to the dairy. There are many factors involved in providing milk with high quality, such as feed quality and herd health, but once milk leaves the teat, the cooling process is very important to safeguard milk quality.

If cooling is done only in a storage tank, the milk might not be cooled down fast enough to maintain its quality. Warm milk is a breeding ground for bacteria, and the amount of bacteria doubles every 20 minutes. Thus, cooling down milk quickly minimizes bacterial growth and safeguards milk quality. By using instant cooling with a heat exchanger directly or shortly after milking, the temperature of the milk can be reduced fast where after the cooled milk can be transported to a storage tank for storage and further cooling.

A chiller can be used to cool down a coolant that circulates between the chiller and the heat exchanger. In some systems, the same coolant is also circulated between the chiller and the storage tank. Thus, the same chiller may be used to instantly cool down the same coolant used both for the heat exchanger and the storage tank.

Summary

The incoming milk to the heat exchanger comes more or less directly from the animals and may have a temperature up to around 37°C. In the heat exchanger, the milk shall be rapidly cooled down to a lower temperature, sometimes about 4°C. The heat exchange process in the heat exchanger is a one-way process of heat transfer from the milk to the coolant. The speed and efficiency of the heat exchange process depends on the temperature difference between the two mediums and the flow rates of the mediums. The coolant needs to have a lower temperature than the desired temperature of the milk after the heat exchange process, to be able to cool down the milk to the desired temperature. However, the milk flow through the heat exchanger might be unstable and there is a risk of freezing the milk in the heat exchanger if the coolant has a temperature below the freezing temperature of the milk. The allowed temperature range for the coolant in the heat exchanger is thus rather narrow, thus between the freezing point of milk and one or two degrees below a desired temperature of the milk, for example 4°C.

In case the same chiller is used to cool down the same coolant used both for the heat exchanger and the storage tank, the chiller has previously been cooling down the coolant to a set temperature based on the allowed temperature range for the coolant in the heat exchanger, to avoid freezing the milk in the heat exchanger. The milk in the storage tank shall be maintained at a constant low temperature, for example around 3.5 °C to 4 °C. The milk coming from the heat exchanger into the storage tank is sought to have a temperature around 4 °C, but in reality the temperature might fluctuate, and be higher, because of a varying milk flow. The temperature difference between the coolant and the milk in the storage tank is small compared to the temperature difference between the coolant and the milk in the heat exchanger, and thus the heat exchange between the milk and the coolant in the storage tank is rather slow and small. The amount of milk in the storage tank is also normally rather large. The chiller then has to be operated for a long time to cool down the milk in the storage tank.

It is an object of the present disclosure to alleviate at least some of the drawbacks with the prior art. Thus, it is an object of the present disclosure to provide a dual cooling system that efficiently cools down milk in the dual cooling system. It is a further object to provide a dual cooling system that also has an efficient heat exchange process between the coolant and the milk in the storage tank. It is a further object of the disclosure to provide a dual cooling system that can adapt to various cooling needs in the overall cool down process of the milk.

These object and others are at least partly achieved by the dual cooling system and method for operating a dual cooling system according to the independent claims, and by the embodiments according to the dependent claims. According to a first aspect, the disclosure relates to method for operating a dual cooling system configured for cooling milk. The dual cooling system comprises a first coolant circuit arranged for circulating coolant, wherein the first coolant circuit comprises a heat exchanger configured for heat exchange between milk and the coolant, and a second coolant circuit for circulating the coolant, wherein the second coolant circuit comprising a storage tank configured for heat exchange between milk and the coolant. The dual cooling system also comprises a chiller comprising a refrigerant circuit configured for heat exchange between a refrigerant and the coolant. The dual cooling system further comprises a fluid control arrangement arranged to selectively direct coolant from the chiller to the first cooling circuit comprising the heat exchanger and to the second cooling circuit comprising the storage tank. The method comprises: controlling a temperature of the coolant based on a first set temperature upon the coolant being directed from the chiller to the first coolant circuit comprising the heat exchanger, and controlling the temperature of the coolant based on a second set temperature, upon the coolant being directed from the chiller to the second coolant circuit comprising the storage tank, wherein the first set temperature and the second set temperature differ.

The method provides efficient cooling of milk in the dual cooling system. Hence, by changing the set temperature for the chiller depending on if the coolant is used for cooling milk in the heat exchanger or is used for cooling milk in the storage tank, the coolant can be cooled down to a lower temperature when it is used for the storage tank, compared to when it is used for the heat exchanger. Thereby efficient cooling may be achieved in both the heat exchanger and the storage tank, while the risk of freezing of milk in the heat exchanger is reduced.

In some embodiments, the method comprises automatically controlling the temperature of the coolant based on the first set temperature, in response to obtaining information indicating that milk in the heat exchanger needs to be cooled down. Thus, the dual cooling system can operate independently of an operator.

In some embodiments, the method comprises automatically controlling the temperature of the coolant based on the second set temperature, in response to obtaining information indicating that milk in the storage tank needs to be cooled down and upon the condition that there is no information obtained indicating that milk in the heat exchanger needs to be cooled down being fulfilled.

Thus, the dual cooling system gives precedence to cooling milk in the heat exchanger independently of input from an operator.

In some embodiments, the method comprises directing coolant from the chiller to the first coolant circuit, in response to obtaining information indicating that milk in the heat exchanger needs to be cooled down. Thus, milk in the heat exchanger can be instantly cooled down.

In some embodiments, the method comprises directing coolant from the chiller to the second coolant circuit, in response to obtaining information indicating that milk in the milk storage tank needs to be cooled down, and upon the condition that there is no information obtained indicating that milk in the heat exchanger needs or will need to be cooled down being fulfilled. Thus, the dual cooling system can cool down milk in the storage tank when there is or will be no need to cool down milk in the heat exchanger.

In some embodiments, the method comprises receiving information from the milking system indicating that milk in the heat exchanger needs to be cooled down. Thus, the heat exchanger or milking system automatically indicates when it needs coolant to cool down milk in the heat exchanger.

In some embodiments, the method comprises receiving information from the storage tank indicating that milk in the storage tank needs to be cooled down. Thus, the storage tank automatically indicates when it needs coolant to cool down milk in the storage tank.

In some embodiments, the fluid control arrangement is arranged to direct coolant from the chiller to either only the first coolant circuit, or only the second coolant circuit. Thus, the coolant is not directed to both the heat exchanger and the storage tank at the same time. As an alternative, coolant is directed to both the first coolant circuit and the second coolant circuit, and the method comprises controlling a temperature of the coolant based on a first set temperature upon the coolant being directed from the chiller to the first coolant circuit comprising the heat exchanger, and controlling the temperature of the coolant based on a second set temperature, upon the coolant being directed from the chiller only to the second coolant circuit comprising the storage tank.

In some embodiments, the first set temperature and the second set temperature differ with at least 4°C, 5°C or 6°C. Thus, the coolant can be cooled down to different temperatures depending on where to it is directed.

In some embodiments, the first set temperature is higher than a freezing temperature of the milk, but lower than 4°C, and the second set temperature is lower than the freezing temperature of the milk. Thus, the coolant can be cooled down to a lower temperature when being directed to the storage tank compared to when being directed to the heat exchanger.

According to a second aspect, the disclosure relates to a dual cooling system configured for cooling milk. The dual cooling system comprises a first coolant circuit arranged for circulating coolant, wherein the first coolant circuit comprises a heat exchanger configured for heat exchange between milk and the coolant, and a second coolant circuit for circulating the coolant, wherein the second coolant circuit comprising a storage tank configured for heat exchange between milk and the coolant. The dual cooling system also comprises a chiller comprising a refrigerant circuit configured for heat exchange between a refrigerant and the coolant. The dual cooling system further comprises a fluid control arrangement arranged to selectively direct coolant from the chiller to the first cooling circuit comprising the heat exchanger and to the second cooling circuit comprising the storage tank. The dual cooling system further comprises a control circuitry configured to control the chiller to control a temperature of the coolant based on a first set temperature upon the coolant being directed from the chiller to the first coolant circuit comprising the heat exchanger. The control circuitry is further configured to control the chiller to control the temperature of the coolant based on a second set temperature, upon the coolant being directed from the chiller to the second coolant circuit comprising the storage tank, wherein the first set temperature and the second set temperature differ.

In some embodiments, the control circuitry is configured to: automatically control the temperature of the coolant based on a first set temperature, in response to obtaining information indicating that milk in the heat exchanger needs to be cooled down.

In some embodiments, the control circuitry is configured to: automatically control the temperature of the coolant based on the second set temperature, in response to obtaining information indicating that milk in the storage tank needs to be cooled down.

In some embodiments, the control circuitry is configured to receive information from a milking system indicating that milk in the heat exchanger needs to be cooled down.

In some embodiments, the control circuitry is configured to receive information from the storage tank indicating that milk in the storage tank needs to be cooled down.

In some embodiments, the control circuitry is configured to control the fluid control arrangement to direct coolant from the chiller to the first coolant circuit, in response to obtaining information indicating that milk in the heat exchanger needs to be cooled down.

In some embodiments, the control circuitry is configured to control the fluid control arrangement to direct coolant from the chiller to the second coolant circuit, in response to obtaining information indicating that milk in the heat exchanger needs or will need to be cooled down, and upon the condition that there is no information obtained indicating that milk in the heat exchanger needs or will need to be cooled down being fulfilled.

According to a third aspect, the disclosure relates to a computer program comprising instructions to cause the dual cooling system according to any of the embodiments of the second aspect, to execute the steps of the method according to any one of the embodiments of the first aspect.

According to a fourth aspect, the disclosure relates to a computer-readable medium having stored thereon the computer program of the third aspect.

Brief description of the drawings

Fig. 1 illustrates a milking arrangement including a dual cooling system according to a first embodiment. Fig. 2 illustrates a cooling circuit of a chiller according to some embodiments.

Fig. 3 is a flow chart of a method for operating a dual cooling system according to some embodiments of the disclosure.

Fig. 4 illustrates a dual cooling system according to a second embodiment.

Detailed description

In the following disclosure, embodiments of a dual cooling system and methods for operating a dual cooling system will be explained. The dual cooling system is configured to change a set temperature used by the chiller for cooling the coolant depending on if the coolant is directed to the heat exchanger or to the storage tank. The dual cooling system is thus configured to apply different set temperatures depending on where to the cooling fluid is being directed, thus, in which circuit it is circulating. As the amount of milk in the storage tank often is large and the storage tank often is arranged to agitate the milk in the storage tank, the coolant can be cooled down to a lower temperature than the freezing point of the milk without having a risk of freezing the milk in the storage tank, when the coolant is used for cooling milk in the storage tank. The coolant can then more efficiently cool down the milk in the storage tank as the temperature difference between the coolant and the milk in the storage tank is increased. Thereby the cooling of the milk in the storage tank can be made faster, and the chiller has to operate less time. There will then be more time for cleaning the chiller while it is not operating.

A dual cooling system is a type of cooling system arranged to cool down milk in both at least one heat exchanger and in at least one storage tank using a chiller.

A heat exchanger is for example a plate heat exchanger (PFIE). A PFIE typically comprises a series of thin stainless-steel plates (or other suitable metals). The coolant flows on one side of the plates while milk flows on the other side of the plates. Fleat is transferred from the milk to the coolant via the plates. The capacity of the PFIE is adjusted by adding or subtracting plates.

A storage tank is a tank arrange to store and cool down milk. It is typically made of stainless steel and is often insulated to reduce the risk of external heat warming up the milk. It also comprises some kind of arrangement for moving around the milk in the tank, such as one or more agitators or agitating nozzles. A chiller is an apparatus arranged to cool down a coolant to be used for cooling milk in one or more heat exchangers and or more storage tanks. The chiller comprises a refrigerant circuit, and because of the duality of the system the chiller is included in several coolant circuits. The chiller typically works by vapour compression or vapour absorption. The chiller has some basic components such as an evaporator, a compressor, a condenser, an expansion unit and a refrigerant. In the evaporator, the refrigerant evaporates and takes heat out of the coolant. These basic components may be scaled up to a plurality of evaporators, a plurality of compressors, a plurality of condensers and/or a plurality of expansion units. However, in the following disclosure the chiller has been exemplified with only one component of each for ease of explanation, which should not be seen as limiting for the disclosure.

A coolant is a fluid having a suitably low freezing temperature. For example, the fluid may comprise a mixture of water and an anti-freeze agent. The anti-freeze agent is for example glycol, for example propylene glycol such as mono propylene glycol (MPG). Thereby the coolant may be cooled down to sub-zero degrees Celsius by the refrigerant without the risk of freezing.

In the following examples of dual cooling systems will be described with reference to Figs. 1 , 2 and 4. Fig. 3 illustrates a flow chart of a method than can be implemented for operating for example the illustrated dual cooling systems.

Fig. 1 illustrates a milking arrangement. The milking arrangement comprises a dual cooling system 1 according to a first embodiment, and a milking system 40. The dual cooling system 1 is arranged in a milk path downstream the milking system 40. The milking system 40 is arranged for extracting milk from at least one animal. The milking system 40 may be an automatic milking system, AMS, comprising a robot arm (not shown) for automatic attachment of teat cups 43 to the teats of animals. Alternatively, the milking system 40 is a milking system wherein teat cups are manually attached to the teats of the animals. The milking system 40 is configured for extracting milk from the teats of animals standing in a milking parlour (not shown). The milking parlour may be configured for housing one or more animals simultaneously. The milking system 40 comprises teat cups 43 and a vacuum system 44 operated in a known manner. Milk extracted in the milking system 40 is led via a conduit 45 to the milk storage tank 3. The milking system 40 comprises a milk pump 41 configured to produce a milk flow from the milking system

40 towards the milk storage tank 3. Milk may be collected in a container 42 of the milking system 40, from which container 42 the milk is pumped by the milk pump

41 towards the milk storage tank 3. In embodiments wherein the milking system 40 comprise an AMS, for one animal, the container 42 may be an end unit or a receiver, where from milk is pumped by the milk pump 41 after milking of an animal has ended. In embodiments wherein the milking system 40 is configured for milking several animals at once, the container 42 may be a balance tank. Milk may be pumped from the balance tank by the milk pump 41 once the balance tank is filled to a certain degree. The balance tank may be provided with a level sensor to detect the level of milk in the tank. The latter type of milking system may be a milking system wherein teat cups are attached manually to the animals, or a larger automatic milking system. The milking system 40 is connected with the dual cooling system by means of a conduit 45.

The dual cooling system 1 comprises a first coolant circuit 51 , a second coolant circuit 52, a chiller 4, a fluid control arrangement and control circuitry 5. The dual cooling system 1 is arranged in a milk path downstream the milking system 40. The first coolant circuit 51 is arranged for circulating coolant. The first coolant circuit 51 comprises a heat exchanger 2 configured for heat exchange between milk and the coolant. The second coolant circuit 52 is also arranged for circulating the coolant. The second coolant circuit 52 comprises a milk storage tank 3 configured for heat exchange between milk and the coolant. The chiller 4 comprises a refrigerant circuit 53 configured for heat exchange between a refrigerant and the coolant. The fluid control arrangement is arranged to selectively direct coolant from the chiller 4 to the first cooling circuit 51 comprising the heat exchanger 2 and to the second cooling circuit 52 comprising the milk storage tank 3. The fluid control arrangement is a mechanism that directs the flow of coolant to any of the circuits 51 , 52. The fluid control arrangement thus controls the fluid flow in the circuits 51 , 52. In the illustrated example, the fluid control arrangement comprises two valve units 9, 10. However, the fluid control arrangement may comprise more or less valves in different configurations of the fluid control arrangement. When the coolant circulates in any of the coolant circuits 51 , 52, the coolant may cool the milk flow from the milking system 40 while the coolant simultaneously is cooled by the refrigerant in the refrigerant circuit 53.

The first coolant circuit 51 comprises a fluid path comprising a cooling path 4a in the chiller 4, a first cooling path 2a in the heat exchanger, a first conduit 11a and a second conduit 11b. The coolant can thus circulate in the fluid path of the first coolant circuit 51 . The coolant is cooled in the cooling path 41 in the chiller 4 by means of heat exchange with the refrigerant. The cooled coolant is then passed via the first conduit 11a to the first cooling path 2a of the heat exchanger 2, where it absorbs heat via heat exchange with milk flowing in a fluid path 2b for milk. Thereafter the coolant is passed via the second conduit 11 b back to the cooling path 4a, where it is cooled down again. The refrigerant circuit 53 thus indirectly cools down the milk in the heat exchanger 2, by means of the coolant. A first valve unit 9 is arranged to the first conduit 11 a. The first valve unit 9 is arranged to control a flow rate of coolant in the first coolant circuit 51 . The first valve unit 9 comprises for example a motorized valve. The valve is for example an on/off vale. The fluid path 2b for milk is part of the milk fluid path between the milking system 40 and the milk storage tank 3. A portion of the first coolant circuit 51 is thus arranged in the milk fluid path.

The second coolant circuit 52 comprises a fluid path comprising the cooling path 4a in the chiller 4, a second cooling path 3a in the milk storage tank, a third conduit 12a, a fourth conduit 12b and parts of the first conduit 11a and a second conduit 11 b connecting the third conduit 12a and the fourth conduit 12b to the cooling path 4a in the chiller 4. More in detail, the conduit 12a is fluidly connected to the first conduit 11 a upstream the first valve unit 9 and to an inlet port 17 of the milk storage tank 3. The third conduit 12a is thus fluidly connected between the first conduit 11a upstream the first valve unit 9 and the inlet port 17 of the milk storage tank 3. In an alternative implementation, the third conduit 12a is connected to the outlet port 31 directly, instead of being connected to the first conduit 11a upstream the first valve unit 9. The first conduit 11 a and the third conduit 12a are then both fluidly connected to the outlet port 31. The fourth conduit 12b is connected to the outlet 18 of the milk storage tank 3 and to the second conduit 11b. The fourth conduit 12b is thus fluidly connected between the outlet 18 of the milk storage tank 3 and to the second conduit 11 b. Alternatively the fourth conduit 12b is connected directly to the inlet port 32 of the chiller 4 instead of to the second conduit 11b. The second conduit 11 b and the fourth conduit 12b are then both fluidly connected to the inlet port 32. A second valve unit 10 is arranged to the third conduit 12a.

The coolant can thus circulate in the fluid path of the second coolant circuit 51 . The coolant is cooled in the cooling path 41 in the chiller 4 by means of heat exchange with the refrigerant. The cooled coolant is then passed via the third conduit 12a to the second cooling path 3a of the milk storage tank 3, where it absorbs heat via heat exchange with milk in the milk storage tank 3. Thereafter, the coolant is passed via the fourth conduit 12b back to the cooling path 41 , where it is cooled down again. The refrigerant circuit 53 thus indirectly cools down the milk in the storage tank 3, by means of the coolant. A first valve unit 9 is arranged to the first conduit 11a. A second valve unit 10 is arranged to the first conduit 11a. The second valve unit 10 is arranged to control a flow rate of coolant in the third conduit 12a. The second valve unit 10 comprises for example a motorized valve. The valve is for example an on/off vale.

The coolant may be circulated in any of the first coolant circuit 51 and the second coolant circuit 52 (and any additional coolant circuit 52’, see Fig. 4), but only in one circuit at a time. Careful control of the valves 9, 10 makes sure that the coolant only circulates in one coolant circuit 51 , 52 at a time. The fluid control arrangement, thus the first valve unit 9 and the second valve unit 10, is arranged to selectively direct coolant from the chiller 4 to the first cooling circuit 51 comprising the heat exchanger 2 and to the second cooling circuit 52 comprising the milk storage tank 3. In detail, the control circuitry 5 is configured to control the first valve 51 and the second valve 52 to allow or stop a flow of coolant in any of the circuits 51 , 52. In some embodiments, the control circuitry 5 is configured to direct coolant from the chiller 4 to the first coolant circuit 51 , in response to obtaining information indicating that milk in the heat exchanger 2 needs to be cooled down. This directing is accomplished by controlling the first valve 9 to open whereby the coolant can flow freely in the first coolant circuit 51 , and the second valve 10 to close whereby the coolant cannot flow in the second coolant circuit 52. In some embodiments the milking system 40 is configured to generate information, for example a first signal or data message, that milk that needs to be cooled down is coming in to (or arriving at) the heat exchanger 2. In some embodiments, the milking system 40 is configured to generate information, for example a second signal or data message, that milk has stopped coming in (ceased to arrive) to the heat exchanger 2. In some embodiments, the control circuitry is configured to direct coolant from the chiller 4 to the second coolant circuit 52, in response to obtaining information indicating that milk in the milk storage tank 3 needs to be cooled down. This directing of the coolant to the second coolant circuit 51 is performed upon the condition that there is no information obtained indicating that milk in the heat exchanger 2 needs or will need to be cooled down being fulfilled. If such information is received, then the coolant is directed to the first coolant circuit 51 and not to the second coolant circuit 52, even if the milk in the milk storage tank 3 also need to be cooled. The directing into the second coolant circuit 52 is accomplished by controlling the first valve 9 to close and the second valve 10 to open, thereby opening for coolant to flow in the second coolant circuit 52. Thus, by selectively direct is meant to direct the coolant to either the first cooling path 2a, or to the second cooling path 3a. For example, to alternatingly direct the coolant to the first cooling path 2a and to the second cooling path 3a. Thus, when the coolant is directed to the first cooling path 2a, it does not pass any second fluid path 3a of a milk storage tank 3, it is only passed to the first cooling path 2a. Also, when the coolant is directed to the second cooling path 3a, it does not pass any first fluid path 2a of a heat exchanger 2, it is only passed to the second cooling path 3a. The fluid control arrangement, thus the first valve 9 and the second valve 10, is controlled by control signals provided by the control circuitry 5.

The chiller 4 also comprises an outlet port 31 and an inlet port 32. The inlet port 32 connects the coolant path 4a with the first conduit 11a and the second conduit 11 b. In some embodiments, the chiller 4 comprises a separate control unit 6. During the heat exchange between the refrigerant and the coolant in the refrigerant circuit 53, the coolant is cooled by the refrigerant and the refrigerant is heated by the coolant. The refrigerant circuit 53 as such may be automatically controlled in a commonly known manner. The heat exchanger 2 comprises an inlet port 15 and an outlet port 16. The inlet port 15 and an outlet port 16 connect the first cooling path 2a with the first conduit 11a and the second conduit 11b. The heat exchanger 2 further comprises a first milk path 2b for circulating milk. If the heat exchanger is a PHE, the first cooling path 2a and the first milk path 2b are for example separated by plates. A heat exchange between the milk and the coolant is obtained along the extent of the first cooling path 2a and the other first milk path 2b. In the heat exchange between the coolant and the milk, the milk is cooled and the coolant is heated. The milk may be cooled substantially to the milk storage temperature by the coolant.

The milk storage tank 3 comprises the second cooling path 3a arranged to circulate coolant provided from the chiller 4. The milk storage tank 3 comprises an inlet port 17 and an outlet port 18. The inlet port 17 connects the second cooling path 3a with the third conduit 12a and the fourth conduit 12b. The milk storage tank 3 comprises milk to be cooled. The milk may have been pre-cooled in the heat exchanger 2 and then directed directly from the heat exchanger 2 to the milk storage tank 3 via the fluid conduit 46. A heat exchange between the milk and the coolant is obtained along the extent of the second cooling path 3a and the milk in the milk storage tank 3. In the heat exchange between the coolant and the milk, the milk is cooled and the coolant is heated. The milk may be cooled substantially to the milk storage temperature by the coolant. The milk storage tank 3 also comprises an agitation arrangement (not shown) configured to mix the milk so that it is more evenly cooled down. The milk storage tank 3 also comprises a control unit 8. The control unit 8 is configured to detect that milk in the milk storage tank 3 needs to be cooled down. Upon such detection, the control unit 8 is configured to notify the control circuitry 5 that milk needs to be cooled down in the milk storage tank 3. The notification is for example a signal or data message. For example, a temperature sensor 20 is arranged to continuously or continually sense the temperature of the milk in the milk storage tank 3 and to provide it to the control unit 8. The control unit 8 compares the sensed temperature with predetermined one or more predetermined temperatures and detects when milk needs to be cooled down. In some embodiments, when a temperature of the milk in the milk storage tank 3 goes below a predetermined temperature, a third signal or data message is generated. When the temperature of the milk in the milk storage tank 3 reaches or exceeds predetermined temperature, a fourth signal or data message is generated. The control unit 8 may include a processor, memory and a communication interface for receiving and sending signals and/or data. In the milk storage tank 3 the milk is stored at a storage temperature. The storage temperature may be within a range of 2 - 5°C, or 2 - 7°C, or approximately 4°C, depending e.g. on local conditions and legislation.

The control circuitry 5 may be a dedicated controller for the dual cooling system 1 . Alternatively, the control circuitry 5 may form part of a control unit of the milking system 40 (not shown) and/or a control unit 6 of the chiller 4 and/or a control unit 8 of the milk storage tank 3. The control circuitry 5 may comprise two or more separate control units 5, 6, 8, each of the control units being configured to control separate parts of the milking arrangement. The one or more separate control units may be configured to communicate with each other or to operate independently of each other without communicating with each other. The control circuitry 5 comprises a processor 5a, memory 5b and a communication interface 5c. The processor 5a comprises one or more processing units, such as one or more Central Processing Units (CPUs). The memory 5b comprises one or more memory units. The communication interface 5c is configured for communication of signals and/or data to and from the control circuitry 5, in order to control and monitor operation of the dual cooling system 1. The communication interface 5c may also comprise a user interface (not shown). The user interface may be a remote user interface. The user interface may comprise an input device such as a touch screen, keyboard or microphone. The control circuitry 5 may also be at least partly be remotely distributed, e.g. to “a cloud server”. Data may then be communicated via the communication interface to the cloud, or directly from sensors to the cloud. The data may then be processed in the cloud (cloud computing), and control data or signals sent back to the control circuitry 5. Thus, dual cooling system 1 may be controlled via control circuitry 5 such as a programmable logic controller (PLC), an edge computer, the cloud server, a Personal Computer (PC), a smart device, etc. The control circuitry 5 is arranged to send control signals to the various components of the chiller 4 such as the pump 27, the compressor 22 etc., and to the valve devices 9, 10, 10’ (Fig. 4) via its communication interface 5c in order to control their functions (in some embodiments via the control unit 6). The control circuitry 5 is also arranged to receive monitored, sensed or measured signals from the chiller 4 (in some embodiments via the control unit 6), signals and/or data from the milking system 40 and from the control unit 8 of the milk storage tank 3, via its communication interface 5c. The control circuitry 5 is configured to separately read the information from the milking system 40 and the information from the control unit 8 of the milk storage tank 3. The control circuitry 5 is configured to control a cool down process of the coolant in the chiller 4. The control circuit 5 is also arranged to provide a fluid flow of coolant in any of the coolant circuits 51 , 51 by means of a pump 27 (see Fig. 2). In some embodiments, the control circuitry 5 is configured to receive information, for example a first signal or data message, from the milking system 40 that milk is incoming to the heat exchanger 2 that needs or will need to be cooled down. In some embodiments, the control circuitry 5 is configured to receive information, for example a second signal or data message, from the milking system 40 that milk has stopped coming to the heat exchanger 2. In some embodiments, the control circuit 5 is configured to receive information, for example a third signal or data message, from the milk storage tank 3 that the temperature of the milk in the storage tank has reached or is above a predetermined threshold. In some embodiments, the control circuit 5 is configured to receive information, for example a fourth signal or data message, from the milk storage tank 3 that the temperature of the milk in the milk storage tank 3 is at or below the predetermined threshold. In some embodiments, the control circuitry 5 is arranged to provide an indication to an operator of the current cooling process of the dual cooling system 1 . For example, the temperature of the coolant, and where the coolant is directed. The indication may be transmitted to the operator as sound, electronic message etc., via the user interface. The indication may alternatively be transmitted to a smart device such as a mobile phone of the user.

Fig. 2 illustrates a refrigerant circuit 53 of the chiller 4, and coolant path 4a being part of the first coolant circuit 51 and the second coolant circuit 52. The refrigerant circuit 53 is arranged to circulate a refrigerant. The refrigerant circuit 53 comprises an evaporator 21 , a compressor 22, a condenser 23 and an expansion valve 25. A first refrigerant conduit 33b is connected between a refrigerant outlet of the evaporator 21 and an inlet of the condenser 23. A second refrigerant conduit 33c is connected between an outlet of the condenser 23 and a refrigerant inlet of the evaporator 21 . The coolant path 4a comprises the evaporator 21 , a tank 26 and a pump 27. A first coolant conduit 33a is connected to the inlet port 31 and a coolant inlet of the evaporator 21 . A second coolant conduit 33f is connected to a coolant outlet of the evaporator 21 and an inlet of the tank 26. A third coolant conduit 33g is connected to an outlet of the tank 26 and an inlet of the pump 27. A fourth coolant conduit 33h is connected to an outlet of the pump 27 and to the outlet port 32. A first temperature sensor 34 is arranged to sense the OUT-temperature of the coolant. A second temperature sensor 29 is arranged to sense the temperature of the coolant in the tank 26. A third temperature sensor 28 is arranged to sense the IN-temperature of the coolant.

In the evaporator 21 , the refrigerant is evaporated and consequently takes heat from the coolant. The refrigerant is thereafter passed to the condenser 23. The compressor 22 uses a gas pump to create low pressure in the evaporator 21 (low temperature) and high pressure in the condenser 23. In the condenser 23 the refrigerant condenses. The heat in the gas is released to air or to another medium, and the gas turns into liquid. A fan 24 may be used to remove heated air. The expansion valve 25 gives the same amount of refrigerant, in a liquid form, back to the evaporator 21 as the compressor 22 takes out as a gas.

The coolant is provided at the inlet port 31 from the thereto connected second conduit 11 b or fourth conduit 12b. In the evaporator 21 , heat is taken from the coolant whereby it is cooled down. The coolant is thereafter collected in the tank 26. The pump 27 pumps the coolant from the tank 26 to the outlet port 32, and to the thereto connected first conduit 11a or third conduit 12a (Fig. 1 ).

The temperature of the coolant is controlled based on the OUT-temperature of the coolant. The OUT-temperature is for example measured with the first temperature sensor 34 or the second temperature sensor 29. Based on the OUT- temperature of the coolant, the compressor 22 is switched on and off. The OUT- temperature is compared to a set-temperature. If the OUT-temperature has reached or is above the set-temperature, the compressor 22 is switched on and the coolant is cooled down. If the OUT-temperature is at or below the set-temperature, the compressor 22 is switched off.

The set temperature differs depending on where to the coolant is directed. In more detail, the control circuitry 5 is configured to control the chiller 4 to control a temperature of the coolant based on a first set temperature upon the coolant being directed from the chiller 4 to the first coolant circuit 51 comprising the heat exchanger 2. Further, the control circuitry 5 is configure to control the chiller 4 to control the temperature of the coolant based on a second set temperature, upon the coolant being directed from the chiller 4 to the second coolant circuit 52 comprising the milk storage tank 3, wherein the first set temperature and the second set temperature differ. As previously explained, the coolant is directed to the first coolant circuit 51 or the second coolant circuit based on received information. In order to control the temperature of the coolant to the first set temperature or the second set temperature, the control circuitry 5 can rely on the same information.

In order to mention a few examples, the coolant circuit 53 may comprise the coolant in an amount within a range of 20-1000 litres, or within a range of 20-200 litres, or within a range of 40-120 litres. The amount of coolant may suitably be selected based on the expected milk flow from the milking system 40 to the milk storage tank 3. The dual cooling system 1 is typically designed for the expected peak flow of milk expected from the milk pump 41 pumping milk into the heat exchanger 2. Several hundreds of litres may be used in milking arrangements comprising a milking parlour wherein many animals, such as e.g. 20-100 animals, are milked simultaneously, which results in a high milk flow to the milk storage tank 3. The lower exemplified ranges of coolant suffice in milking arrangements where only one animal at a time or only a few animals are milked simultaneously. The cooling capacity in the refrigerant circuit 53 is adapted to the expected milk flow and depends inter alia on the number of animals milked simultaneously in the milking system 40. A coolant flow matched to the milk flow will make the heat exchanger 2 easier to size and will make efficient use of the coolant. A typical coolant-to-milk ratio is 3: 1 , however 2:1 or 1 .5: 1 may also be adequate.

According to some embodiments, the control circuitry 5 stores a computer program in the memory 5b comprising instructions which, when the program is executed by the processor 5a, cause a dual cooling system to carry out a method as illustrated in Fig. 3 for operating the dual cooling system. The dual cooling system is for example any one of the dual cooling systems as explained herein. The computer program is in some embodiments stored on a computer-readable medium such as a memory, for example a flash memory.

In the following embodiments of the method for operating the dual cooling system 1 will be explained with reference to the flow chart in Fig. 3. The method describes to control the temperature of the coolant differently based on whether the coolant is cooling milk in the heat exchanger 2 or in the milk storage tank 3. Thus, the method describes to control the temperature in different ways depending on where to the coolant is directed, for example, depending on which cooling circuit the coolant is circulated in. In some embodiments, the method comprises obtaining information that milk in the heat exchanger 2 and/or milk in the milk storage tank 3 needs or will need to be cooled down. In some embodiments, the method comprises receiving SOa information from the milking system 40 indicating that milk in the heat exchanger 2 needs to be cooled down. For example, the milking system 40 is sending a first signal, for example when the pump 41 starts pumping or when the level in the tank 52 goes beyond a first level, or by other means, to the control circuitry 5 that milk in the heat exchanger 2 needs to be cooled. The control circuitry 5 is receiving the information via its communication interface 5c. Thus, the control circuitry 5 is configured to receive information from the milking system 40 indicating that milk in the heat exchanger 2 needs to be cooled down.

In some other embodiments, the method comprises receiving SOa information from the milk storage tank 3 indicating that milk in the milk storage tank 3 needs to be cooled down. For example, the control unit 8 of the milk storage tank 3 is sending a third signal to the control circuitry 5 that milk in the milk storage tank 3 needs to be cooled. The control circuitry 5 is receiving the information via its communication interface 5c. Thus, the control circuitry 5 is configured to receive information from the milk storage tank 3 indicating that milk in the milk storage tank 3 needs to be cooled down.

Depending on whether the coolant is used for cooling down milk in the heat exchanger 2 or is used for cooling down milk in the milk storage tank 3, the set temperature for the coolant is different. Thus, different set temperatures are configured, thus used. Thus, in some embodiments, the method includes determining whether the coolant is being directed to the first coolant circuit 51 . This is for example the case if information has been received that milk in the heat exchanger 2 needs to be cooled, and no information has been obtained, for example received, that cooling of the milk in the heat exchanger can be stopped. In some embodiments, in response to obtaining information indicating that milk in the heat exchanger 2 needs to be cooled down, the method comprises directing S1a coolant from the chiller 4 to the first coolant circuit 51 . In other words, the fluid flow in the first coolant circuit 51 is opened, and the fluid flow in the second circuit 52 is stopped (if any). In some embodiments, the directing includes opening the first valve device 9 and closing the second valve device 10 (if not already closed). Another indication that the coolant is being directed to the first coolant circuit 51 is thus that the present configuration of the fluid control arrangement, thus that first valve device 9 is open and the second valve device 10 is closed. Then coolant will flow to the heat exchanger 2. The coolant shall then be cooled down based on the first set temperature. The control circuitry 5, for example the unit 6 of the chiller 4, controls the refrigerant circuit 53 accordingly, thus, compares the OUT-temperature with the first set-temperature and controls the compressor 22 accordingly as known in the art. In other words, the method comprises controlling S1 a temperature of the coolant based on the first set temperature upon the coolant being directed from the chiller 4 to the first coolant circuit 51 comprising the heat exchanger 2. Thus, at times when the coolant is used for cooling milk in the heat exchanger 2, the coolant is cooled down based on the first set temperature.

However, if it is revealed that the coolant is directed to the second coolant circuit 52 of the milk storage tank 3, the coolant shall then be cooled down based on the second set temperature. This is for example the case if information has been received that milk in the milk storage tank 3 needs or will need to be cooled down, and no information has been received that the milk in the heat exchanger 2 needs or will need to be cooled. In some embodiments, in response to obtaining information indicating that milk in the storage tank 3 needs to be cooled down, and upon the condition that there is no information obtained indicating that milk in the heat exchanger needs or will need to be cooled down being fulfilled, the method comprises directing S2a the coolant from the chiller 4 to the second coolant circuit 52. In other words, the fluid flow in the second coolant circuit 52 is opened, and the fluid flow in the first circuit 51 is stopped (if any). In some embodiments, if information is received that milk in the heat exchanger soon need to be cooled down, for example within a time period of 0 (zero) to 10 minute, such as within one or two minutes, then the coolant will not be directed to the second coolant circuit 52. Instead it will be directed to the first coolant circuit 51 , or it will wait until the coolant shall be directed to the first coolant circuit 51 , and then direct the coolant to that circuit 51. Thereby there will be less delay in cooling the milk in the heat exchanger 2. In some embodiments, the directing includes closing the first valve device 9 and opening the second valve device 10. Another indication that the coolant is being directed to the second coolant circuit 52 is thus the present configuration of the fluid control arrangement, thus that first valve device 9 is closed, and the second valve device 10 is open. Then coolant will then flow to the milk storage tank 3. The control circuitry 5, for example the control unit 6 of the chiller 4, controls the refrigerant circuit 53 accordingly, thus, compares the OUT-temperature with the second set-temperature and controls the compressor 22 accordingly. Thus, the method further comprises controlling S2 the temperature of the coolant based on the second set temperature, upon the coolant being directed from the chiller 4 to the second coolant circuit 52 comprising the milk storage tank 3, and upon the condition that there is no information obtained indicating that milk in the heat exchanger needs or will need to be cooled down being fulfilled. Thus, if the coolant is used for cooling milk in the milk storage tank 3, the coolant is cooled down based on the second set temperature. Hence, in some embodiments, cooling milk in the heat exchanger 2 has higher priority than cooling milk in the milk storage tank 3. Thus, upon information is received SOa indicating that milk in the heat exchanger 2 needs to be cooled down, the coolant will be used for cooling down milk in the heat exchanger 2 even if information from the milk storage tank 3 indicating that milk in the milk storage tank 3 needs to be cooled down is received or if the milk in the milk storage tank 3 is being cooled with the same coolant. However, if no information has been received indicating that milk in the heat exchanger needs to be cooled down being fulfilled, and SOb information from the milk storage tank 3 indicating that milk in the milk storage tank 3 needs to be cooled down is received, the coolant will be used for cooling down milk in the milk storage tank 3. In other words, verifying that no coolant is circulating in the first circuit 51 , before the coolant is started circulating in any other coolant circuit 52.

The first set temperature is typically higher than a freezing temperature of the milk, but lower than for example 4°C. The second set temperature is typically lower than the freezing temperature of the milk. The freezing temperature of milk is for the majority of cows between -0.525°C to -0.565°C, with an average temperature of about -0.540°C. For example, the first set temperature is a temperature in an interval between -0.5°C to 4°C, in an interval between -0.5°C to 2 °C, or in an interval between -0.5°C to 1°C. Generally, if the milk is to be cooled down to a certain temperature in the heat exchanger 2, for example 4°C, then the coolant should be approximately two degrees cooler, thus 2°C. The second set temperature is for example between -5°C to -7°C. Thus, the first set temperature and the second set temperature differ with at least 4°C, 5°C or 6°C.

In some embodiments, the method comprises automatically controlling S1 the temperature of the coolant based on the first set temperature, in response to obtaining information indicating that milk in the heat exchanger 2 needs to be cooled down. Thus, upon the control circuitry 5 is receiving information from the milking system 40 that milk in the heat exchanger 2 needs to be cooled, the control circuitry 5 in response is controlling the components of the chiller 4 according to the first set temperature, including the compressor 22 and the pump 27, such that the first set temperature is used for controlling the OUT-temperature of the coolant. The refrigerant circuit 53 is the controlled accordingly, thus, the OUT-temperature is compared with the first set temperature and the compressor 22 is controlled accordingly. Thus, the control circuitry 5 is configured to automatically control the temperature of the coolant based on a first set temperature, in response to obtaining information indicating that milk in the heat exchanger 2 needs to be cooled down. To automatically control means to control without manual intervention. In some embodiments, the controlling S1 comprises directing S1a the coolant to the first fluid path 2a. In some embodiments, the directing comprises controlling the first valve unit 9 to open and the second valve unit 10 to close. In some embodiments, the method comprises automatically controlling S2 the temperature of the coolant based on the second set temperature, in response to obtaining information indicating that milk in the milk storage tank 3 needs to be cooled down. Thus, upon the control circuitry 5 is receiving information from the milking system 40 that milk in the storage tank 2 needs to be cooled, the control circuitry 5 in response is controlling the components of the chiller 4 according to the second set temperature, including the compressor 22 and the pump 27, such that the second set temperature is used for controlling the OUT-temperature of the coolant. The refrigerant circuit 53 is the controlled accordingly, thus, the OUT-temperature is compared with the second set-temperature and the compressor 22 is controlled accordingly. Thus, the control circuitry 5 is configured to automatically control the temperature of the coolant based on the second set temperature, in response to obtaining information indicating that milk in the milk storage tank 3 needs to be cooled down. In some embodiments, the controlling S2 comprises directing S2a the coolant to the second fluid path 3a. In some embodiments, the directing comprises controlling the second valve unit 10 to open and the first valve unit 9 to close.

According to some embodiments, the method comprises starting circulation of coolant in the first coolant circuit 51 , in response to receiving a first signal from the milking system 40 that milking has started. The milking system 40 thereafter at some point in time stops the milking and sends a second signal to the control circuitry 5 that the milking has stopped. In response to such signal, the method comprises stopping circulation of coolant in the first coolant circuit 51. In this manner the circulation of coolant in the first coolant circuit 51 is started in response to the first signal and stopped once milk flow has stopped. The first signal is related to commencement or increase of a milk flow from the milking system 40 towards the milk storage tank 3. The first signal may be triggered in response to at least one of a number of different events, states, or occasions in the milking arrangement, which event, state, or occasion relates directly or indirectly to the commencement or increase of a milk flow from the milking system 40. The method may thus include starting circulation of coolant in the first coolant circuit 51 in response to the first signal. This may be achieved by controlling the pump 27 comprising simple on and off switching of the pump, which rotate/s at a constant speed. Alternatively, the pump speed may be controlled to provide a variable flow rate of coolant.

In the following non-exhaustive examples of triggering the first signal are listed:

- According to some embodiments, the first signal may correlate with a start or increase of pumping of milk from the milking system 40 towards the milk storage tank 2. The first signal may be provided when the milk pump 41 of the milking system 40 is started, or a predetermined time period before or after the milk pump 41 is started.

- According to some embodiments, the first signal may relate to a time period until commencement or increase of the milk flow from the milking system 40. There are a number of events in a milking system 40 which preceded a milk flow from the milking system 40, which events occur within a predefined period of a start of milk flow. The time period need not be an exact time period but may be an approximate time period. Just to mention a few, such events may be one or more animals entering or leaving a milking parlour, a gate of a milking parlour opening or closing, feed being distributed to an animal in a milking parlour, a teat cup being attached to a teat of an animal, etc.

- According to some embodiments, the first signal may relate to an animal approaching or entering an automatic milking system, AMS. Determining that an animal approaches or enters an AMS may e.g. be done by a camera, by detecting that a gate is opening or closing, by determining that feed is being distributed to the animal, just to name a few.

- According to embodiments, wherein the milking system 40 comprises a balance tank for intermediate storage of milk prior to being conducted to the milk storage tank 3, the first signal may relate to a filling degree of the balance tank. A certain filling degree of the balance tank (i.e. the volume of milk stored in the tank) may namely trigger start of milk being pumped from the milking system 40. The balance tank may be a container 42, as illustrated in Fig. 1. According to these embodiments, the circulation of coolant in the first coolant circuit 41 may be controlled based on the filling degree of the balance tank, such that an increase in the filling degree of the balance tank results in an increase in the circulation of coolant in the coolant circuit. This may be done stepless (i.e. continuously) or stepwise, e.g. that at predefined threshold levels of the degree of filling the capacity of the cooling apparatus is increased by increasing the circulation of coolant in the first coolant circuit 41. Similarly, at a decreasing degree of filling of the balance tank the circulation of coolant in the coolant circuit may be decreased, stepless or stepwise.

- In one and the same milking arrangement the first signal may be triggered by not only one event but by different events, which may depend on the current operating condition of the milking system 40.

As an illustrative example, the first signal relating to commencement of a milk flow may be related to starting the pump 41. When the pump 41 is not pumping milk, the milk flow is off and the circulation of coolant in the first coolant circuit 41 is not yet started. When the pump 41 starts pumping milk, the first signal is generated and the circulation of the coolant in the first coolant circuit 41 is started in response to the first signal. That includes to start pumping with the pump 27, cool down the coolant based on the first set temperature, opening the first valve 9 and closing the second valve 10. Any of the events listed herein as triggering the first signal may be an indication of a cooling need in the heat exchanger 2, and thus trigger use of the first set temperature. An event may be an actual milk flow, or a predicted milk flow. A cooling need may thus be a predicted cooling need that will occur at a certain time in the future or within a certain time period, and the first signal may thus indicate such a predicted cooling need. The circulation of coolant in the first coolant circuit 41 may be maintained at a predetermined flow rate. When the milk pump stops, the second signal is generated and the circulation of the coolant in the first coolant circuit 41 is stopped in response to the second signal. When a temperature of the milk in the milk storage tank 3 goes below a predetermined temperature, a third signal is generated, and the circulation of the coolant in the second coolant circuit 42 is started in response to the third signal, if the coolant is not being circulated in the first coolant circuit 41. That is, a first signal has been generated but not yet a second signal. The circulation of coolant in the second coolant circuit 42 includes start pumping with the pump 27, to cool down the coolant based on the second set temperature closing the first valve 9 and opening the second valve 10. When a temperature of the milk in the milk storage tank 3 reaches, exceeds or is above the predetermined temperature, a fourth signal is generated, and the circulation of the coolant in the second coolant circuit 42 is stopped. If, during circulation of coolant in the second coolant circuit 42, a first signal is received, the circulation of coolant in the second coolant circuit 42 is stopped and the circulation of coolant in the first coolant circuit 41 is started. The circulation of coolant is thus switched from the second coolant circuit 42 to the first coolant circuit 41 .

Fig. 4 illustrates a dual cooling system 1 according to a second embodiment. The dual cooling system 1 according to the second embodiment comprises the same components as described in relation to the first embodiment in Fig. 1. In addition, the dual cooling system 1 according to the second embodiment comprises an additional milk storage tank 3’ and thus an additional second coolant circuit 52’. The function is the same as the milk storage tank 3 as in the first embodiment, and it receives milk pre-cooled with the heat exchanger 2. The additional milk storage tank 3 is thus arranged to store and cool down milk. The additional second coolant circuit 52’ comprises a fluid path comprising the cooling path 4a in the chiller 4, an additional second cooling path 3a’ in the milk storage tank 3, an additional third conduit 12a’, an additional fourth conduit 12b’ and parts of the first conduit 11a, the second conduit 11 b, the third conduit 12a, and the fourth conduit 12b connecting the additional third conduit 12a’ and the additional fourth conduit 12b’ to the cooling path 4a in the chiller 4. More in detail, the additional milk storage tank 3’ comprises the additional second cooling path 3a’. The additional second cooling path 3a’ is connected to an additional inlet port 17’ and to an additional outlet port 18’ of the additional milk storage tank 3’. A heat exchange process between the milk and the coolant is obtained along the extent of the additional second cooling path 3a and the milk in the additional milk storage tank 3. The additional milk storage tank 3 also comprises an arrangement (not shown) to mix the milk so it becomes more evenly cooled down. The additional milk storage tank 3 also comprises an additional control unit 8’. The additional control unit 8’ is configured to detect that milk in the milk storage tank 3 needs to be cooled down. Upon such detection, the additional control unit 8’ is configured to notify the control circuitry 5 that milk needs to be cooled down in the additional milk storage tank 3’. For example, a temperature sensor (not shown) arranged to sense the temperature of the milk in the additional milk storage tank 3’ may indicate that the temperature of the milk is outside an allowed temperature interval and needs to be cooled down.

The additional third conduit 12a’ is fluidly connected to the third conduit 12a’ upstream the second valve unit 10. The additional third conduit 12a’ is thus fluidly connected between the third conduit 12a upstream the second valve unit 10 and the additional inlet port 17’ of the additional milk storage tank 3’. An additional second valve unit 10’ is arranged to the additional third conduit 12a’. The additional second valve unit 10’ is arranged to control a flow rate of coolant in the additional third conduit 12a’. The additional second valve unit 10’ comprises for example a motorized valve. The valve is for example an on/off vale. By opening the additional valve unit 10’ and closing the two other valves 9, 10, and pumping with the pump 27, coolant will flow in the third coolant circuit 54. The additional fourth conduit 12b’ is connected to the additional outlet port 18’ of the additional milk storage tank 3’ and to the fourth conduit 12a. The additional fourth conduit 12b’ is thus fluidly connected between the additional outlet port 17’ of the additional milk storage tank 3’ and the fourth conduit 12a. As the dual cooling system 1 now comprises two milk storage tanks, a prioritization has to be made which one to cool down if both requests that their milk need cooling. For example, the milk with highest temperature will then be prioritized to be cooled. It should be appreciated that the dual cooling system 1 may include more heat exchangers and more milk storage tanks than the ones illustrated, that will be connected to the chiller 4 in similar ways.

The present disclosure is not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the disclosure, which is defined by the appending claims.