Dual refrigeration system and method of operating a dual refrigeration system

Abstract

A method of operating a dual refrigeration system (1) for cooling milk, the dual refrigeration system comprising a first coolant circuit (51) arranged to circulate a coolant and a second coolant circuit (52) for circulating the coolant, the first coolant circuit (51) comprising a heat exchanger (2) configured for heat exchange between the milk and the coolant, and the second coolant circuit (52) comprising a milk storage tank (3) configured for heat exchange between the milk and the coolant, the dual refrigeration system further comprising a chiller (4) comprising a refrigerant circuit (53) configured for heat exchange between the refrigerant and the coolant, and a fluid control device (9, 10, 10') arranged to selectively direct the coolant from the chiller (4) to the first coolant circuit (51) comprising the heat exchanger (2) and to the second coolant circuit (52) comprising the milk storage tank (3). The method includes controlling (S1) the temperature of the coolant based on a first set temperature when the coolant is guided from the chiller (4) to a first coolant circuit (51) comprising a heat exchanger (2), and controlling (S2) the temperature of the coolant based on a second set temperature when the coolant is guided from the chiller (4) to a second coolant circuit (52) comprising a milk storage tank (3), the first set temperature and the second set temperature being different. The present disclosure also relates to a corresponding dual cooling system.

Description

[Technical Field]

[0001] The present disclosure relates to techniques for cooling milk, and in particular to a dual cooling system that includes a chiller that cools the coolant used to cool the milk both in a heat exchanger and in a tank. [Background technology]

[0002] Milk collected on the farm must be cooled quickly to avoid bacterial growth. To deliver high-quality milk, the milk must be of high quality when it arrives at the dairy farm. While there are many factors involved in providing high-quality milk, such as the quality of the feed and the health of the herd, the cooling process after the milk leaves the teats is crucial to protecting the quality of the milk.

[0003] Cooling only in the storage tank may not cool the milk quickly enough to maintain its quality. Warm milk is a breeding ground for bacteria, and bacterial load doubles every 20 minutes. Therefore, cooling the milk quickly minimizes bacterial growth and protects its quality. Instant cooling using a heat exchanger directly or immediately after milking can rapidly reduce the milk's temperature. The cooled milk can then be transported to a storage tank for storage and further cooling.

[0004] A chiller can be used to cool the coolant circulating 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 can be used to instantly cool the same coolant used in both the heat exchanger and the storage tank. Summary of the Invention

[0005] The milk entering the heat exchanger is typically supplied directly from the animal and may have a maximum temperature of approximately 37°C. In the heat exchanger, the milk is rapidly cooled, sometimes to temperatures as low as approximately 4°C. The heat exchange process in the heat exchanger is a one-way heat transfer process from the milk to the coolant. The speed and efficiency of the heat exchange process depend on the temperature difference between the two media and the flow rate of the media. To ensure that the milk can be cooled to the desired temperature, the coolant temperature must be lower than the desired temperature of the milk after the heat exchange process. However, if the coolant temperature is lower than the freezing point of the milk, the flow of milk through the heat exchanger may become unstable, posing a risk of the milk freezing within the heat exchanger. Therefore, the acceptable temperature range of the coolant in the heat exchanger is quite narrow, i.e., between the freezing point of the milk and a temperature 1-2 degrees lower than the desired temperature of the milk (e.g., 4°C).

[0006] When the same coolant is used in both the heat exchanger and the storage tank, the coolant is cooled to a preset temperature based on the allowable temperature range of the coolant in the heat exchanger to prevent the milk from freezing in the heat exchanger. The milk in the storage tank needs to be maintained at a constant low temperature, for example, around 3.5°C to 4°C. The milk flowing from the heat exchanger into the storage tank is required to be at a temperature of around 4°C, but in reality, the temperature may fluctuate and become higher due to changes in the flow of milk. Because the temperature difference between the coolant and milk in the storage tank is smaller than the temperature difference between the coolant and milk in the heat exchanger, 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 usually quite large. Therefore, the cooler must be operated for a long time to cool the milk in the storage tank.

[0007] It is an object of the present disclosure to alleviate at least some of the drawbacks of the prior art. Accordingly, it is an object of the present disclosure to provide a dual cooling system that efficiently cools milk within the dual cooling system. A further object is to provide a dual cooling system that also has an efficient heat exchange process between the coolant in the storage tank and the milk. A further object of the present disclosure is to provide a dual cooling system that can adapt to various cooling needs throughout the milk cooling process.

[0008] These objects and others are achieved at least in part by a dual refrigeration system and a method for operating a dual refrigeration system according to the independent claims and by embodiments according to the dependent claims.

[0009] According to a first aspect, the present disclosure relates to a method of operating a dual refrigeration system configured to cool milk. The dual refrigeration system includes a first coolant circuit arranged to circulate a coolant and a second coolant circuit for circulating the coolant, the first coolant circuit including a heat exchanger configured for heat exchange between the milk and the coolant, and the second coolant circuit including a milk storage tank configured for heat exchange between the milk and the coolant. The dual refrigeration system also includes a chiller including a refrigerant circuit configured for heat exchange between the refrigerant and the coolant. The dual refrigeration system further includes a fluid control device arranged to selectively direct coolant from the chiller to the first cooling circuit including the heat exchanger and the second cooling circuit including the storage tank. The method includes controlling the temperature of the coolant based on a first set temperature when the coolant is directed from the chiller to the first coolant circuit including the heat exchanger, and controlling the temperature of the coolant based on a second set temperature when the coolant is directed from the chiller to the second coolant circuit including the storage tank, the first set temperature and the second set temperature being different.

[0010] This method efficiently cools the milk in a dual cooling system. Therefore, by changing the set temperature of the chiller depending on whether the coolant is used to cool the milk in the heat exchanger or in the storage tank, the coolant can be cooled to a lower temperature when used in the storage tank compared to when used in the heat exchanger. This allows efficient cooling to be achieved in both the heat exchanger and the storage tank, while reducing the risk of the milk freezing in the heat exchanger.

[0011] In some embodiments, the method includes automatically controlling the temperature of the coolant based on the first set temperature in response to obtaining information indicating a need to cool the milk in the heat exchanger. Thus, the dual cooling system can operate independently of an operator.

[0012] In some embodiments, the method includes automatically controlling the temperature of the coolant based on a second set temperature in response to obtaining information indicating that the milk in the storage tank needs to be cooled and when a condition is met that information indicating that the milk in the heat exchanger needs to be cooled has not been obtained.

[0013] Thus, the dual cooling system preferentially cools the milk within the heat exchanger independent of operator input.

[0014] In some embodiments, the method includes directing coolant from a chiller to a first coolant circuit in response to obtaining information indicating that the milk in the heat exchanger needs to be cooled, thereby instantaneously cooling the milk in the heat exchanger.

[0015] In some embodiments, the method includes directing coolant from the chiller to the second coolant circuit in response to obtaining information indicating that the milk in the storage tank needs to be cooled and when a condition is met that information indicating that the milk in the heat exchanger needs or will need to be cooled has not been obtained. Thus, the dual cooling system is able to cool the milk in the storage tank when cooling the milk in the heat exchanger is not needed or will not be needed.

[0016] In some embodiments the method includes receiving information from the milking system indicating that the milk in the heat exchanger needs to be cooled, such that the heat exchanger or milking system automatically indicates when coolant is needed to cool the milk in the heat exchanger.

[0017] In some embodiments, the method includes receiving information from the storage tank indicating that the milk in the storage tank needs to be cooled, such that the storage tank automatically indicates when coolant is needed to cool the milk in the storage tank.

[0018] In some embodiments, the fluid control device is arranged to direct coolant from the chiller either only to the first coolant circuit or only to the second coolant circuit, thereby preventing coolant from being directed to both the heat exchanger and the storage tank simultaneously. Alternatively, coolant is directed to both the first coolant circuit and the second coolant circuit, and the method includes controlling the temperature of the coolant based on a first setpoint temperature when the coolant is directed from the chiller to the first coolant circuit with the heat exchanger, and controlling the temperature of the coolant based on a second setpoint temperature when the coolant is directed from the chiller to only the second coolant circuit with the storage tank.

[0019] In some embodiments, the first set temperature and the second set temperature differ by at least 4° C., 5° C., or 6° C. Thus, the coolant can be cooled to different temperatures depending on where it is directed.

[0020] In some embodiments, the first set point temperature is above the freezing temperature of the milk but below 4° C., and the second set point temperature is below the freezing temperature of the milk. Thus, the coolant may be cooled to a lower temperature when directed to the storage tank compared to when directed to the heat exchanger.

[0021] According to a second aspect, the present disclosure relates to a dual refrigeration system configured for cooling milk. The dual refrigeration system includes a first coolant circuit arranged to circulate a coolant and a second coolant circuit for circulating the coolant, the first coolant circuit including a heat exchanger configured for heat exchange between the milk and the coolant, and the second coolant circuit including a milk storage tank configured for heat exchange between the milk and the coolant. The dual refrigeration system also includes a chiller including a refrigerant circuit configured for heat exchange between the refrigerant and the coolant. The dual refrigeration system further includes a fluid control device arranged to selectively direct coolant from the chiller to the first cooling circuit including the heat exchanger and the second cooling circuit including the storage tank. The dual refrigeration system further includes a control circuit configured to control the chiller to control the temperature of the coolant based on a first set temperature when the coolant is directed from the chiller to the first coolant circuit including the heat exchanger. The control circuit is further configured to control the chiller to control the temperature of the coolant based on a second set temperature when the coolant is directed from the chiller to a second coolant circuit having a storage tank, where the first set temperature and the second set temperature are different.

[0022] In some embodiments, the control circuit is configured to automatically control the temperature of the coolant based on the first set temperature in response to obtaining information indicating that the milk in the heat exchanger needs to be cooled.

[0023] In some embodiments, the control circuit is configured to automatically control the temperature of the coolant based on the second set temperature in response to obtaining information indicating that the milk in the storage tank needs to be cooled.

[0024] In some embodiments the control circuit is configured to receive information from the milking system indicating that the milk in the heat exchanger needs to be cooled.

[0025] In some embodiments, the control circuit is configured to receive information from the storage tank indicating that the milk in the storage tank needs to be cooled.

[0026] In some embodiments, the control circuit is configured to control the fluid control device to direct coolant from the chiller to the first coolant circuit in response to obtaining information indicating that the milk in the heat exchanger needs to be cooled.

[0027] In some embodiments, the control circuit is configured to control the fluid control device to direct coolant from the chiller to the second coolant circuit in response to obtaining information indicating that the milk in the heat exchanger needs or will need to be cooled and when a condition is met that information indicating that the milk in the heat exchanger needs or will need to be cooled has not been obtained.

[0028] According to a third aspect, the present disclosure relates to a computer program comprising instructions for causing a dual cooling system according to any of the embodiments of the second aspect to perform the steps of the method according to any of the embodiments of the first aspect.

[0029] According to a fourth aspect, the present disclosure relates to a computer readable medium having stored thereon the computer program of the third aspect. [Brief explanation of the drawings]

[0030] [Figure 1] 1 shows a milking implement including a dual cooling system according to a first embodiment; [Figure 2] 1 illustrates a cooling circuit of a chiller according to some embodiments. [Figure 3] 1 is a flowchart of a method of operating a dual cooling system according to some embodiments of the present disclosure. [Figure 4] 2 shows a double cooling system according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0031] The following disclosure describes embodiments of a dual refrigeration system and a method for operating a dual refrigeration system. The dual refrigeration system is configured to change the setpoint temperature used by the chiller to cool the coolant depending on whether the coolant is being directed to the heat exchanger or the storage tank. In this way, the dual refrigeration system is configured to apply different setpoint temperatures depending on where the cooling fluid is being directed and, therefore, the circuit through which it circulates. Because the amount of milk in the storage tank is often large and is often arranged to stir the milk in the storage tank, when a coolant is used to cool the milk in the storage tank, the coolant can be cooled to a temperature below the freezing point of the milk without risking the milk in the storage tank freezing. Furthermore, because the temperature difference between the coolant and the milk in the storage tank is large, the coolant can cool the milk in the storage tank more efficiently. This allows the milk in the storage tank to cool faster and shortens the operation time of the chiller. This also provides more time for cleaning the chiller while it is not operating.

[0032] A dual cooling system is a type of cooling system that is arranged to use chillers to cool milk in both at least one heat exchanger and at least one storage tank.

[0033] The heat exchanger may be, for example, a plate heat exchanger (PHE). A PHE typically comprises a series of thin stainless steel plates (or other suitable metal). Coolant flows over one side of the plates and milk flows over the other side of the plates. Heat is transferred from the milk to the coolant through the plates. The capacity of the PHE is adjusted by adding or removing plates.

[0034] A storage tank is a tank arranged to store and cool milk. It is usually made of stainless steel and is often insulated to reduce the risk of external heat warming the milk. It also contains some kind of device, such as one or more agitators or stirring nozzles, for moving around the milk in the tank.

[0035] A chiller is a device arranged to cool a coolant used to cool milk in one or more heat exchangers and / or one or more storage tanks. The chiller comprises a refrigerant circuit, and due to the dual nature of the system, the chiller is included in several coolant circuits. Typically, chillers function by vapor compression or vapor absorption. They have several basic components, such as an evaporator, a compressor, a condenser, an expansion unit, and a refrigerant. In the evaporator, the refrigerant evaporates, removing heat from the coolant. These basic components may be scaled up to multiple evaporators, multiple compressors, multiple condensers, and / or multiple expansion units. However, in the following disclosure, for ease of explanation, the chillers are illustrated with only one component each, and this should not be considered as limiting the disclosure.

[0036] The coolant is a fluid that has a suitably low freezing temperature. For example, the fluid may comprise a mixture of water and an antifreeze. The antifreeze may be, for example, a glycol, e.g., propylene glycol, such as monopropylene glycol (MPG), so that the coolant can be cooled to below freezing by the refrigerant without risk of freezing.

[0037] The following example dual refrigeration system is described with reference to Figures 1, 2, and 4. Figure 3 shows a flowchart of a method that may be implemented, for example, to operate the illustrated dual refrigeration system.

[0038] FIG. 1 shows a milking apparatus. The milking apparatus comprises a double cooling system 1 according to a first embodiment and a milking system 40. The double cooling system 1 is arranged in the milk path downstream of the milking system 40. The milking system 40 is arranged to extract milk from at least one animal. The milking system 40 may be an automatic milking system (AMS) comprising a robotic arm (not shown) for automatically attaching teat cups 43 to the teats of the animal. Alternatively, the milking system 40 is a milking system in which the teat cups are manually attached to the teats of the animal. The milking system 40 is configured to extract milk from the teats of an animal standing in a milking parlor (not shown). The milking parlor may be configured to accommodate one or more animals simultaneously. The milking system 40 comprises teat cups 43 and a vacuum system 44, which are operated in a known manner. The milk extracted by the milking system 40 is conducted to a milk storage tank 3 via a conduit 45. The milking system 40 comprises a milk pump 41 configured to generate a flow of milk from the milking system 40 to the milk storage tank 3. Milk may be collected in a container 42 of the milking system 40, from which the milk is pumped by the milk pump 41 towards the milk storage tank 3. In embodiments in which the milking system 40 comprises an AMS, the container 42 may be an end unit or receptacle for a single animal, from which the milk pump 41 pumps milk after the animal has finished milking. In embodiments in which the milking system 40 is configured to milk multiple animals at a time, the container 42 may be a balance tank. Milk may be pumped from the balance tank by the milk pump 41 when the balance tank is partially filled. The balance tank may be provided with a level sensor to detect the level of milk in the tank. This latter type of milking system may be a milking system in which teat cups are manually attached to the animals, or a larger, automatic milking system. The milking system 40 is connected to a dual cooling system by a conduit 45.

[0039] The dual cooling system 1 comprises a first coolant circuit 51, a second coolant circuit 52, a chiller 4, and a fluid control and control circuit 5. The dual cooling system 1 is arranged in the milk path downstream of the milking system 40. The first coolant circuit 51 is arranged to circulate a 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 to circulate a 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 the refrigerant and the coolant. The fluid control is arranged to selectively direct the 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 is a mechanism for directing the flow of the coolant to one of the circuits 51, 52. Thus, the fluid control device controls the flow of fluid in the circuits 51, 52. In the example shown, the fluid control device comprises two valve units 9, 10. However, the fluid control device may comprise more or fewer valves in different configurations of the fluid control device. When coolant circulates through either of the coolant circuits 51, 52, it may cool the milk flow from the milking system 40 at the same time as being cooled by the refrigerant in the refrigerant circuit 53.

[0040] The first coolant circuit 51 comprises a fluid path including the cooling path 4a in the chiller 4, the first cooling path 2a in the heat exchanger, a first conduit 11a, and a second conduit 11b. Thus, a coolant can circulate through the fluid path of the first coolant circuit 51. The coolant is cooled in the cooling path 41 in the chiller 4 by heat exchange with a refrigerant. The cooled coolant is then sent via the first conduit 11a to the first cooling path 2a of the heat exchanger 2, where it absorbs heat through heat exchange with milk flowing through the milk fluid path 2b. The coolant is then returned via the second conduit 11b to the cooling path 4a, where it is cooled again. Thus, the refrigerant circuit 53 indirectly cools the milk in the heat exchanger 2 by the coolant. A first valve unit 9 is arranged in the first conduit 11a. The first valve unit 9 is arranged to control the flow rate of the coolant in the first coolant circuit 51. The first valve unit 9 comprises, for example, an electrically operated valve. For example, the valve is an on / off valve. The fluid path 2b for milk is part of the milk fluid path between the milking system 40 and the milk storage tank 3. Thus, part of the first coolant circuit 51 is arranged in the milk fluid path.

[0041] The second coolant circuit 52 comprises a fluid path comprising the cooling path 4a in the chiller 4, the 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 the second conduit 11b connecting the third conduit 12a and the fourth conduit 12b to the cooling path 4a in the chiller 4. More particularly, the conduit 12a is fluidly connected to the first conduit 11a upstream of the first valve unit 9 and to the inlet port 17 of the milk storage tank 3. The third conduit 12a is therefore fluidly connected between the first conduit 11a upstream of 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 directly to the outlet port 31 instead of being connected to the first conduit 11a upstream of the first valve unit 9. The first conduit 11 a and the third conduit 12 a are then both fluidly connected to the outlet port 31. The fourth conduit 12 b is connected to the outlet 18 of the milk storage tank 3 and to the second conduit 11 b. Thus, the fourth conduit 12 b is fluidly connected between the outlet 18 of the milk storage tank 3 and the second conduit 11 b. Alternatively, the fourth conduit 12 b is connected directly to the inlet port 32 of the chiller 4 instead of the second conduit 11 b. Then, both the second conduit 11 b and the fourth conduit 12 b are fluidly connected to the inlet port 32. A second valve unit 10 is arranged in the third conduit 12 a.

[0042] In this way, the coolant can circulate through the fluid path of the second coolant circuit 51. The coolant is cooled by heat exchange with the refrigerant in the cooling path 41 in the chiller 4. The cooled coolant is then sent via the third conduit 12a to the second cooling path 3a in the milk storage tank 3, where it absorbs heat through heat exchange with the milk in the milk storage tank 3. The coolant is then returned via the fourth conduit 12b to the cooling path 41, where it is cooled again. Thus, the refrigerant circuit 53 indirectly cools the milk in the storage tank 3 by means of the coolant. A first valve unit 9 is arranged in the first conduit 11a. A second valve unit 10 is arranged in the first conduit 11a. The second valve unit 10 is arranged to control the flow rate of the coolant in the third conduit 12a. For example, the second valve unit 10 comprises an electrically operated valve. For example, the valve is an on / off valve.

[0043] Coolant can be circulated in either the first coolant circuit 51 or the second coolant circuit 52 (as well as any additional coolant circuits 52', see Figure 4), but only in one circuit at a time. Close control of the valves 9, 10 ensures that coolant is circulated through only one of the coolant circuits 51, 52 at a time. The fluid control device, and hence the first valve unit 9 and second valve unit 10, are arranged to selectively direct coolant from the chiller 4 to the first cooling circuit 51 comprising the heat exchanger 2 and the second cooling circuit 52 comprising the milk storage tank 3. In particular, the control circuit 5 is configured to control the first valve 51 and the second valve 52 to allow or stop the flow of coolant in either of the circuits 51, 52. In some embodiments, the control circuit 5 is configured to direct coolant from the chiller 4 to the first coolant circuit 51 in response to obtaining information indicating that the milk in the heat exchanger 2 needs to be cooled. This is achieved by controlling the first valve 9 to be open to allow the coolant to flow freely through the first coolant circuit 51 and the second valve 10 to be closed to prevent the coolant from flowing through the second coolant circuit 52. In some embodiments, the milking system 40 is configured to generate information, e.g. a first signal or data message, that milk requiring cooling is flowing into (or reaching) the heat exchanger 2. In some embodiments, the milking system 40 is configured to generate information, e.g. a second signal or data message, that milk is no longer flowing into (reaching) the heat exchanger 2. In some embodiments, the control circuit is configured to direct the coolant from the chiller 4 to the second coolant circuit 52 in response to receiving information indicating that the milk in the milk storage tank 3 needs to be cooled. This directing of the coolant to the second coolant circuit 51 is performed when the condition is met that no information has been received indicating that the milk in the heat exchanger 2 needs or will need to be cooled. If such information is received, the coolant is directed to the first coolant circuit 51 rather than the second coolant circuit 52, even though the milk in the milk storage tank 3 also needs to be cooled.The induction of coolant into the second coolant circuit 52 is achieved by controlling the first valve 9 to close and the second valve 10 to open, thereby allowing the coolant to flow into the second coolant circuit 52. Therefore, selective induction means guiding the coolant into either the first cooling path 2a or the second cooling path 3a. For example, it means alternately guiding the coolant into the first cooling path 2a and the second cooling path 3a. Therefore, when the coolant is induced into the first cooling path 2a, it does not pass through the second fluid path 3a of the milk storage tank 3, but only through the first cooling path 2a. Also, when the coolant is induced into the second cooling path 3a, it does not pass through the first fluid path 2a of the heat exchanger 2, but only through the second cooling path 3a. The fluid control device, and therefore the first valve 9 and the second valve 10, are controlled by control signals provided by the control circuit 5.

[0044] The chiller 4 also comprises an outlet port 31 and an inlet port 32. The inlet port 32 connects the coolant path 4a to the first conduit 11a and the second conduit 11b. In some embodiments, the chiller 4 comprises a separate control unit 6. During heat exchange between the refrigerant and the coolant in the refrigerant circuit 53, the coolant is cooled by the refrigerant and the coolant is heated by the refrigerant. Such a refrigerant circuit 53 can be automatically controlled in a known manner.

[0045] The heat exchanger 2 has an inlet port 15 and an outlet port 16. The inlet port 15 and the outlet port 16 connect the first cooling path 2a to the first conduit 11a and the second conduit 11b. The heat exchanger 2 further has a first milk path 2b for circulating milk. If the heat exchanger is a PHE, for example, the first cooling path 2a and the first milk path 2b are separated by a plate. Heat exchange between the milk and the coolant is obtained along the length 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 can be substantially cooled to the milk storage temperature by the coolant.

[0046] The milk storage tank 3 includes a second cooling path 3a arranged to circulate the coolant provided by the chiller 4. The milk storage tank 3 includes an inlet port 17 and an outlet port 18. The inlet port 17 connects the second cooling path 3a to the third conduit 12a and the fourth conduit 12b. The milk storage tank 3 contains milk to be cooled. The milk can be pre-cooled in the heat exchanger 2 and then directly guided from the heat exchanger 2 to the milk storage tank 3 via the fluid conduit 46. Heat exchange between the milk and the coolant is achieved along the second cooling path 3a and the temperature of 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 can be substantially cooled to the milk storage temperature by the coolant. The milk storage tank 3 also includes a stirring device (not shown) configured to mix the milk so that the milk is cooled more uniformly. The milk storage tank 3 also includes a control unit 8. The control unit 8 is configured to detect that the milk in the milk storage tank 3 needs to be cooled. Upon such detection, the control unit 8 is configured to notify the control circuit 5 that the milk in the milk storage tank 3 needs to be cooled. The notification is, for example, a signal or a data message. For example, the temperature sensor 20 is arranged to continuously or continuously sense the temperature of the milk in the milk storage tank 3 and provide it to the control unit 8. The control unit 8 compares the sensed temperature with one or more predetermined temperatures to detect when the milk needs to be cooled. In some embodiments, a third signal or data message is generated when the temperature of the milk in the milk storage tank 3 falls below a predetermined temperature. A fourth signal or data message is generated when the temperature of the milk in the milk storage tank 3 reaches or exceeds the predetermined temperature. The control unit 8 may include a processor, a memory, and a communication interface for transmitting and receiving signals and / or data. In the milk storage tank 3, the milk is stored at a storage temperature. The storage temperature may be, for example, in the range of 2-5°C, or 2-7°C, or about 4°C, depending on local conditions and laws.

[0047] The control circuit 5 may be a dedicated controller for the dual cooling system 1. Alternatively, the control circuit 5 may form part of a control unit (not shown) of the milking system 40, and / or the control unit 6 of the chiller 4, and / or the control unit 8 of the milk storage tank 3. The control circuit 5 may comprise two or more separate control units 5, 6, 8, each configured to control a separate part of the milking equipment. 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 circuit 5 comprises a processor 5a, a memory 5b, and a communication interface 5c. The processor 5a may comprise one or more processing units, such as one or more central processing units (CPUs). The memory 5b may comprise one or more memory units. The communication interface 5c is configured to communicate signals and / or data to and from the control circuit 5 for controlling and monitoring the operation of the dual cooling system 1. The communication interface 5c may comprise a user interface (not shown). The user interface may be a remote user interface. The user interface may include input devices such as a touchscreen, keyboard, or microphone. The control circuitry 5 may also be at least partially distributed remotely, for example, on a "cloud server." Data may then be communicated to the cloud via a communication interface or directly from the sensors to the cloud. The data may then be processed in the cloud (cloud computing), and control data or signals may be sent back to the control circuitry 5. Thus, the dual refrigeration system 1 may be controlled via a control circuitry 5 such as a programmable logic controller (PLC), an edge computer, a cloud server, a personal computer (PC), a smart device, or the like. The control circuitry 5 is arranged to send control signals via its communication interface 5c (in some embodiments, via a control unit 6) to various components of the chiller 4, such as the pump 27, the compressor 22, and the valve devices 9, 10, 10' (FIG. 4), to control their functions.The control circuit 5 is also arranged to receive, via its communication interface 5c, monitoring, sensing or measurement signals from the chiller 4 (in some embodiments via the control unit 6), signals and / or data from the control unit 8 of the milking system 40 and the milk storage tank 3. The control circuit 5 is configured to read information from the milking system 40 and information from the control unit 8 of the milk storage tank 3 separately. The control circuit 5 is configured to control the cooling process of the coolant in the chiller 4. The control circuit 5 is also arranged to provide a fluid flow of coolant to either of the coolant circuits 51, 51 by means of the pump 27 (see FIG. 2 ). In some embodiments, the control circuit 5 is configured to receive information, e.g. a first signal or data message, from the milking system 40 that milk is flowing into the heat exchanger 2 that requires or will require cooling. In some embodiments, the control circuit 5 is configured to receive information, e.g. a second signal or data message, from the milking system 40 that milk has stopped flowing into the heat exchanger 2. In some embodiments, the control circuit 5 is configured to receive information, e.g. 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 exceeded a predetermined threshold. In some embodiments, the control circuit 5 is configured to receive information, e.g. 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 below a predetermined threshold. In some embodiments, the control circuit 5 is arranged to provide an operator with an indication of the current cooling process of the dual cooling system 1, e.g. the temperature of the coolant, the location where the coolant is being directed, etc. The indication may be transmitted to the operator via a user interface, as a voice, an electronic message, etc. Alternatively, the indication may be transmitted to a smart device such as the user's mobile phone.

[0048] FIG. 2 shows the refrigerant circuit 53 of the chiller 4 and the coolant path 4a, which is 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 includes an evaporator 21, a compressor 22, a condenser 23, and an expansion valve 25. A first refrigerant conduit 33b is connected between the refrigerant outlet of the evaporator 21 and the inlet of the condenser 23. A second refrigerant conduit 33c is connected between the outlet of the condenser 23 and the refrigerant inlet of the evaporator 21. The coolant path 4a includes the evaporator 21, a tank 26, and a pump 27. A first coolant conduit 33a is connected to the inlet port 31 and the refrigerant inlet of the evaporator 21. A second coolant conduit 33f is connected to the coolant outlet of the evaporator 21 and the inlet of the tank 26. A third coolant conduit 33g is connected to the outlet of the tank 26 and the inlet of the pump 27. A fourth coolant conduit 33h is connected to the outlet of the pump 27 and to the outlet port 32. A first temperature sensor 34 is positioned to sense the OUT temperature of the coolant. A second temperature sensor 29 is positioned to sense the temperature of the coolant in the tank 26. A third temperature sensor 28 is positioned to sense the IN temperature of the coolant.

[0049] In the evaporator 21, the refrigerant evaporates, thereby removing heat from the refrigerant. The refrigerant is then sent to the condenser 23. The compressor 22 uses a gas pump to create low pressure (low temperature) in the evaporator 21 and high pressure in the condenser 23. In the condenser 23, the refrigerant condenses. The heat of the gas is rejected to the air or another medium, causing the gas to become a liquid. A fan 24 may be used to remove the heated air. An expansion valve 25 returns the same amount of refrigerant in liquid form to the evaporator 21 as the compressor 22 removes as a gas.

[0050] The refrigerant is supplied from the second conduit 11b or the fourth conduit 12b connected to the inlet port 31. In the evaporator 21, the refrigerant loses heat and is cooled. The refrigerant is then collected in the tank 26. The pump 27 pumps the refrigerant from the tank 26 to the outlet port 32 and to the first conduit 11a or the third conduit 12a (FIG. 1) connected thereto.

[0051] The temperature of the refrigerant is controlled based on the OUT temperature of the refrigerant. The OUT temperature is measured, for example, by the first temperature sensor 34 or the second temperature sensor 29. The compressor 22 is turned on or off based on the OUT temperature of the refrigerant. The OUT temperature is compared with a set temperature. If the OUT temperature reaches or exceeds the set temperature, the compressor 22 is switched on and the refrigerant is cooled. If the OUT temperature is equal to or lower than the set temperature, the compressor 22 is switched off.

[0052] The set temperature differs depending on where the coolant is guided. More specifically, the control circuit 5 is configured to control the coolant 4 to control the temperature of the coolant based on a first set temperature when the coolant is guided from the coolant 4 to a first coolant circuit 51 including the heat exchanger 2. Furthermore, the control circuit 5 is configured to control the coolant 4 to control the temperature of the coolant based on a second set temperature when the coolant is guided from the coolant 4 to a second coolant circuit 52 including the milk storage tank 3, where the first set temperature and the second set temperature are different. As explained above, the coolant is guided to the first coolant circuit 51 or the second coolant circuit based on the received information. The control circuit 5 can rely on the same information to control the temperature of the coolant to the first set temperature or the second set temperature.

[0053] To give some examples, the coolant circuit 53 may contain a quantity of coolant in the range of 20 to 1000 liters, or in the range of 20 to 200 liters, or in the range of 40 to 120 liters. The quantity of coolant can be suitably selected based on the expected flow of milk 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 from the milk pump 41, which pumps milk into the heat exchanger 2. In milking installations with milking parlours, hundreds of liters may be used. In these milking parlours, many animals, e.g., 20 to 100 animals, are milked simultaneously, resulting in a large flow of milk to the milk storage tank 3. In milking installations where only one animal or only a few animals are milked simultaneously, a coolant in the lower ranges exemplified is sufficient. The cooling capacity of the refrigerant circuit 53 is adapted to the expected flow of milk and depends, inter alia, on the number of animals milked simultaneously in the milking system 40. Matching the coolant flow to the milk flow facilitates sizing of the heat exchanger 2 and results in efficient use of the coolant. A typical coolant to milk ratio is 3:1, although a 2:1 or 1.5:1 ratio may also be sufficient.

[0054] According to some embodiments, the control circuit 5 stores a computer program in the memory 5b, which includes instructions that, when executed by the processor 5a, cause the dual refrigeration system to perform a method for operating a dual refrigeration system such as that shown in Figure 3. The dual refrigeration system may be, for example, any of the dual refrigeration systems described herein. The computer program, in some embodiments, is stored in a computer-readable medium such as a memory, for example, a flash memory.

[0055] The following embodiment of a method for operating the dual cooling system 1 will be described with reference to the flow chart of Figure 3. The method describes controlling the temperature of the coolant differently depending on whether it is cooling milk in the heat exchanger 2 or in the milk storage tank 3. Thus, the method describes controlling the temperature differently depending on where the coolant is directed, for example depending on the cooling circuit through which the coolant is circulated. In some embodiments, the method comprises obtaining information that the milk in the heat exchanger 2 and / or the milk in the milk storage tank 3 needs or will need to be cooled. In some embodiments, the method comprises receiving information from the milking system 40 indicating that the milk in the heat exchanger 2 needs to be cooled (SOa). For example, the milking system 40 has sent a first signal to the control circuit 5 that the milk in the heat exchanger 2 needs to be cooled, for example when the pump 41 starts pumping, or when the level in the tank 52 exceeds a first level, or by other means. The control circuit 5 has received the information via its communication interface 5c. The control circuit 5 is therefore arranged to receive information from the milking system 40 indicating that the milk in the heat exchanger 2 needs to be cooled.

[0056] In some other embodiments, the method includes receiving (SOa) information from the milk storage tank 3 indicating that the milk in the milk storage tank 3 needs to be cooled. For example, the control unit 8 of the milk storage tank 3 has sent a third signal to the control circuit 5 that the milk in the milk storage tank 3 needs to be cooled. The control circuit 5 has received the information via its communication interface 5c. Thus, the control circuit 5 is configured to receive the information from the milk storage tank 3 indicating that the milk in the milk storage tank 3 needs to be cooled.

[0057] Depending on whether the coolant is used to cool milk in the heat exchanger 2 or in the milk storage tank 3, different setpoint temperatures for the coolant are configured and therefore used. Accordingly, in some embodiments, the method includes determining whether coolant is being directed to the first coolant circuit 51. This may be the case, for example, if information is received that the milk in the heat exchanger 2 needs to be cooled, but information that cooling of the milk in the heat exchanger can be stopped is not obtained, e.g., not received. In some embodiments, the method includes directing (S1a) coolant from the chiller 4 to the first coolant circuit 51 in response to obtaining information indicating that the milk in the heat exchanger 2 needs to be cooled. In other words, the flow of fluid in the first coolant circuit 51 is opened and the flow of fluid (if any) in the second circuit 52 is stopped. 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 coolant is being directed to the first coolant circuit 51 is the current configuration of the fluid control device, i.e., the first valve device 9 is open and the second valve device 10 is closed. The coolant will then flow into the heat exchanger 2. The coolant shall then be cooled based on the first set temperature. The control circuit 5, e.g., unit 6 of the chiller 4, controls the refrigerant circuit 53 accordingly, thus comparing the OUT temperature with the first set temperature and controlling the compressor 22 accordingly, as known in the art. In other words, the method includes controlling (S1) the temperature of the coolant based on the first set temperature once it is directed from the chiller 4 to the first coolant circuit 51 comprising the heat exchanger 2. In this way, the coolant will have been cooled based on the first set temperature by the time it is used to cool milk in the heat exchanger 2.

[0058] However, if coolant is found to be directed to the second coolant circuit 52 of the milk storage tank 3, the coolant shall be further cooled based on the second set temperature. This is the case, for example, when information is received that the milk in the milk storage tank 3 needs or will need to be cooled, but information is not 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 the milk in the storage tank 3 needs to be cooled, if the condition is met that information is not obtained that indicates that the milk in the heat exchanger needs or will need to be cooled, the method comprises directing (S2a) coolant from the chiller 4 to the second coolant circuit 52. In other words, the flow of fluid in the second coolant circuit 52 is opened and the flow of fluid (if any) in the first circuit 51 is stopped. In some embodiments, if information is received that the milk in the heat exchanger needs to be cooled immediately, coolant will not be directed to the second coolant circuit 52, for example, within a time period of 0 (zero) to 10 minutes, e.g., within 1 minute or 2 minutes. 3. Instead, it directs it into the first coolant circuit 51, or it waits until coolant is directed into the first coolant circuit 51, and then directs the coolant into that circuit 51. This reduces the delay in cooling the milk in the heat exchanger 2. In some embodiments, the directing comprises closing the first valve device 9 and opening the second valve device 10. Thus, another indication that coolant is being directed into the second coolant circuit 52 is the current configuration of the fluid control devices, so that the first valve device 9 is closed and the second valve device 10 is open. Coolant then flows into the milk storage tank 3. The control circuit 5, for example the control unit 6 of the chiller 4, controls the refrigerant circuit 53 accordingly, and therefore 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 a second set temperature when the coolant is directed from the chiller 4 to the second coolant circuit 52 comprising the milk storage tank 3 and when the condition is met that no information has been obtained indicating that cooling of the milk in the heat exchanger is or will be required.3. In this way, when using coolant to cool the milk in the milk storage tank 3, the coolant is cooled based on the second set temperature. Therefore, in some embodiments, cooling the milk in the heat exchanger 2 has a higher priority than cooling the milk in the milk storage tank 3. Therefore, when information indicating that the milk in the heat exchanger 2 needs to be cooled is received (S0a), the coolant will be used to cool the milk in the heat exchanger 2, even if information indicating that the milk in the milk storage tank 3 needs to be cooled is received from the milk storage tank 3, or if the milk in the milk storage tank 3 is cooled with the same refrigerant. However, if it is satisfied that information indicating that the milk in the heat exchanger needs to be cooled is not received, and if information is received from the milk storage tank 3 indicating that the milk in the milk storage tank 3 needs to be cooled (S0b), the coolant will be used to cool the milk in the milk storage tank. In other words, it is ensured that the coolant is not circulating in the first circuit 51 before starting to circulate in the other coolant circuit 52.

[0059] Typically, the first set temperature is higher than the freezing temperature of milk, but lower, for example, than 4°C. Typically, the second set temperature is lower than the freezing temperature of milk. The freezing temperature of milk for most cows is between -0.525°C and -0.565°C, with an average temperature of about -0.540°C. For example, the first set temperature is between -0.5°C and 4°C, between -0.5°C and 2°C, or between -0.5°C and 1°C. Generally, when cooling milk to a specific temperature (for example, 4°C) in heat exchanger 2, the coolant should be about 2 degrees lower, i.e., 2°C. For example, the second set temperature is between -5°C and -7°C. Therefore, the first set temperature and the second set temperature differ by at least 4°C, 5°C, or 6°C.

[0060] In some embodiments, the method includes automatically controlling (S1) the temperature of the coolant based on a first set temperature in response to obtaining information indicating that the milk in the heat exchanger 2 needs to be cooled. Thus, when the control circuit 5 receives information from the milking system 40 that the milk in the heat exchanger 2 needs to be cooled, in response the control circuit 5 controls the components of the chiller 4, including the compressor 22 and the pump 27, according to the first set temperature, such that the first set temperature is used to control the OUT temperature of the coolant. The refrigerant circuit 53 is controlled accordingly, such that the OUT temperature is compared to the first set temperature and the compressor 22 is controlled accordingly. Thus, the control circuit 5 is configured to automatically control the temperature of the coolant based on the first set temperature in response to obtaining information indicating that the milk in the heat exchanger 2 needs to be cooled. Automatic control means controlling without human intervention. In some embodiments, the control S1 includes directing (S1a) the coolant to the first fluid path 2a. In some embodiments, 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 a second set temperature in response to obtaining information indicating that the milk in the milk storage tank 3 needs to be cooled. Thus, when the control circuit 5 receives information from the milking system 40 that the milk in the storage tank 2 needs to be cooled, in response the control circuit 5 controls the components of the chiller 4, including the compressor 22 and the pump 27, according to the second set temperature, such that the second set temperature is used to control the OUT temperature of the coolant. The refrigerant circuit 53 is controlled accordingly, and thus the OUT temperature is compared to the second set temperature and the compressor 22 is controlled accordingly. Thus, the control circuit 5 is configured to automatically control the temperature of the coolant based on the second set temperature in response to obtaining information indicating that the milk in the milk storage tank 3 needs to be cooled. In some embodiments, controlling (S2) comprises directing (S2a) the coolant to the second fluid path 3a.In some embodiments, directing includes controlling the second valve unit 10 to open and the first valve unit 9 to close.

[0061] According to some embodiments, the method includes initiating the 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 then stops milking at some point and sends a second signal to the control circuit 5 that milking has stopped. In response to such a signal, the method includes stopping the circulation of coolant in the first coolant circuit 51. In this way, the circulation of coolant in the first coolant circuit 51 is initiated in response to the first signal and is stopped when milk flow stops. The first signal is associated with the initiation or increase of milk flow from the milking system 40 towards the milk storage tank 3. The first signal may be activated in response to at least one of a number of different events, conditions, or opportunities in the milking equipment, which events, conditions, or opportunities are directly or indirectly associated with the initiation or increase of milk flow from the milking system 40. Thus, the method may include initiating the circulation of coolant in the first coolant circuit 51 in response to the first signal. This can be achieved by controlling the pump 27, including simply turning the pump on and off to rotate at a constant speed. Alternatively, the pump speed may be controlled to provide a variable flow rate of the coolant.

[0062] The following is a non-exhaustive list of examples of activating the first signal: According to some embodiments, the first signal may be correlated with the start or increase of milk pumping from the milking system 40 to the milk storage tank 2. The first signal may be provided when the milk pump 41 of the milking system 40 is started, or at a predetermined time period before or after the milk pump 41 is started. According to some embodiments, the first signal may relate to the time period leading up to the start or increase of milk flow from the milking system 40. There are a number of events in the milking system 40 that precede the flow of milk from the milking system 40, and these events occur within a predetermined time period of the start of milk flow. The time period does not have to be an exact period, but can be an approximate period. To name just a few, such events may be one or more animals entering or leaving the milking parlor, the opening or closing of a gate to the milking parlor, the dispensing of food to an animal in the milking parlor, the attachment of a teat cup to the teat of an animal, etc. According to some embodiments, the first signal may relate to an animal approaching or entering the automatic milking system AMS. The determination that an animal is entering or has entered the AMS may be made, for example, by detecting the opening or closing of a gate by a camera, determining that the animal is being served food, etc. According to embodiments in which the milking system 40 comprises a balancing tank for intermediate storage of milk before it is transferred to the milk storage tank 3, the first signal may be related to the filling level of the balancing tank. A certain filling level of the balancing tank (i.e. the amount of milk stored in the tank) may trigger the start of pumping milk from the milking system 40. The balancing tank may be a container 42 as shown in FIG. 1. According to these embodiments, the circulation of coolant in the first coolant circuit 41 may be controlled based on the filling level of the balancing tank, such that an increase in the filling level of the balancing tank results in an increase in the circulation of coolant in the coolant circuit. This may be done in a non-stepwise (i.e. continuous) or stepwise manner, for example, so that at a predetermined threshold level of filling, the capacity of the cooling equipment is increased by increasing the circulation of coolant in the first coolant circuit 41. Similarly, when the filling level of the balance tank decreases, the circulation of coolant in the coolant circuit may be reduced in a non-stepwise or stepwise manner. In the same milking implement, the first signal may be activated not only by one event, but by different events which may depend on the current operating state of the milking system 40 .

[0063] As an illustrative example, the first signal related to the initiation of milk flow may be related to the start of 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 has not yet begun. When the pump 41 begins pumping milk, a first signal is generated and the circulation of coolant in the first coolant circuit 41 is initiated in response to the first signal. This includes starting pumping with the pump 27, cooling the coolant based on a first set temperature, opening the first valve 9, and closing the second valve 10. Any of the events listed herein as activating the first signal may be indicative of a need for cooling in the heat exchanger 2 and thus activate the use of the first set temperature. The event may be an actual milk flow or a predicted flow of milk. The need for cooling may therefore be a predicted need for cooling that will occur at a specific time or within a specific period in the future, and the first signal may therefore be indicative of such a predicted need for cooling. The circulation of coolant in the first coolant circuit 41 can be maintained at a predetermined flow rate. When the milk pump stops, a second signal is generated, and in response to the second signal, the circulation of coolant in the first coolant circuit 41 is stopped. When the temperature of the milk in the milk storage tank 3 falls below a predetermined temperature, a third signal is generated, and if coolant is not circulating in the first coolant circuit 41, the circulation of coolant in the second coolant circuit 42 is started in response to the third signal. That is, the first signal has been generated but the second signal has not yet been generated. The circulation of coolant in the second coolant circuit 42 involves closing the first valve 9 and opening the second valve 10, causing the pump 27 to begin pumping and cooling the coolant based on a second set temperature. When the temperature of the milk in the milk storage tank 3 reaches, exceeds, or exceeds the predetermined temperature, a fourth signal is generated, and the circulation of coolant in the second coolant circuit 42 is stopped. When the first signal is received while the coolant is circulating in the second coolant circuit 42, the coolant circulation in the second coolant circuit 42 is stopped and the coolant circulation in the first coolant circuit 41 is started. This switches the coolant circulation from the second coolant circuit 42 to the first coolant circuit 41.

[0064] Figure 4 shows a double cooling system 1 according to a second embodiment. The double cooling system 1 according to the second embodiment comprises the same components as those described with respect to the first embodiment of Figure 1. Furthermore, the double cooling system 1 according to the second embodiment comprises an additional milk storage tank 3' and therefore an additional second coolant circuit 52', the function of which is the same as the milk storage tank 3 as in the first embodiment, and which receives milk that has been pre-cooled in the heat exchanger 2. The additional milk storage tank 3 is therefore arranged to store and cool the milk. The additional second coolant circuit 52' comprises a fluid path including the cooling path 4a in the chiller 4, the additional second cooling path 3a' in the milk storage tank 3, the additional third conduit 12a', the additional fourth conduit 12b', and a portion connecting the additional third conduit 12a' and the additional fourth conduit 12b' of the first conduit 11a, the second conduit 11b, the third conduit 12a, and the fourth conduit 12b to the cooling path 4a in the chiller 4. More specifically, 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 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 additional second cooling path 3a and the milk in the additional milk storage tank 3. The additional milk storage tank 3 also comprises a device (not shown) for mixing the milk so that the milk is cooled more evenly. The additional milk storage tank 3 also comprises an additional control unit 8'. The additional control unit 8' is configured to detect that the milk in the milk storage tank 3 needs to be cooled. Upon such detection, the additional control unit 8' is configured to notify the control circuit 5 that the milk in the additional milk storage tank 3' needs to be cooled. 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 acceptable temperature range and needs to be cooled.

[0065] The additional third conduit 12a' is fluidly connected to the third conduit 12a' upstream of the second valve unit 10. Thus, the additional third conduit 12a' is fluidly connected between the third conduit 12a upstream of the second valve unit 10 and the additional inlet port 17' of the additional milk storage tank 3'. The additional second valve unit 10' is arranged in the additional third conduit 12a'. The additional second valve unit 10' is arranged to control the flow rate of the coolant in the additional third conduit 12a'. The additional second valve unit 10' comprises, for example, an electrically operated valve. For example, the valve is an on / off valve. By opening the additional valve unit 10', closing the other two valves 9, 10, and pumping with the pump 27, the coolant will flow into the third coolant circuit 54. An additional fourth conduit 12b' is connected to an additional outlet port 18' of the additional milk storage tank 3' and to the fourth conduit 12a. Thus, the additional fourth conduit 12b' is fluidly connected between the additional outlet port 17' of the additional milk storage tank 3' and the fourth conduit 12a. Because the dual cooling system 1 currently comprises two milk storage tanks, if both milks require cooling, a priority must be given to which one is cooled. For example, the milk with the highest temperature is cooled first. It will be appreciated that the dual cooling system 1 may include more heat exchangers and milk storage tanks than those shown, connected to the chiller 4 in a similar manner.

[0066] The present disclosure is not limited to the above-described preferred embodiments. Various alternatives, modifications, and equivalents may be used. Therefore, the above-described embodiments should not be construed as limiting the scope of the present disclosure, which is defined by the appended claims.

Claims

1. A method of operating a dual refrigeration system (1) for cooling milk, said dual refrigeration system comprising: a first coolant circuit (51) arranged for circulating a coolant, said first coolant circuit (51) comprising a heat exchanger (2) configured for heat exchange between milk and said coolant; a second coolant circuit (52) for circulating the coolant, the second coolant circuit (52) comprising a milk storage tank (3) configured for heat exchange between milk and the coolant; a chiller (4) comprising a refrigerant circuit (53) configured for heat exchange between a refrigerant and said coolant; a fluid control device (9, 10, 10') 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 method comprises: When the coolant is guided from the chiller (4) to the first coolant circuit (51) including the heat exchanger (2), controlling the temperature of the coolant based on a first set temperature (S1); and (S2) controlling the temperature of the coolant based on a second set temperature when the coolant is guided 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 are different, the first set temperature being higher than the freezing temperature of the milk but lower than 4°C, and the second set temperature being lower than the freezing temperature of the milk.

2. The method comprises:

2. The method of claim 1, comprising automatically controlling (S1) the temperature of the coolant based on the first set temperature in response to obtaining information indicating that the milk in the heat exchanger (2) needs to be cooled.

3. The method comprises:

3. The method of claim 2, further comprising automatically controlling (S2) the temperature of the coolant based on the second set temperature in response to obtaining information indicating that the milk in the milk storage tank (3) needs to be cooled and when a condition is met that information indicating that the milk in the heat exchanger (2) needs to be cooled has not been obtained.

4. 4. The method of claim 2 or 3, comprising directing (S1a) 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.

5. 5. The method according to claim 2, further comprising: directing (S2a) coolant from the chiller (4) to the second coolant circuit (52) in response to obtaining information indicating that the milk in the milk storage tank (3) needs to be cooled and when the condition is met that no information has been obtained indicating that the milk in the heat exchanger (2) needs or will need to be cooled.

6. The method according to any one of claims 2 to 5, comprising receiving (S0) information from a milking system (40) indicating that the milk in the heat exchanger (2) needs to be cooled.

7. The method according to any one of claims 2 to 6, comprising receiving (S0) information from the milk storage tank (3) indicating that the milk in the milk storage tank (3) needs to be cooled.

8. 8. The method according to any one of claims 1 to 7, wherein the fluid control device (9, 10, 10') is arranged to direct coolant from the chiller (4) either only to the first coolant circuit (51) or only to the second coolant circuit (52).

9. 9. The method of any one of claims 1 to 8, wherein the first set temperature and the second set temperature differ by at least 4°C, 5°C, or 6°C.

10. A double cooling system (1) for cooling milk, comprising: a first coolant circuit (51) arranged for circulating a coolant, said first coolant circuit (51) comprising a heat exchanger (2) configured for heat exchange between milk and said coolant; a second coolant circuit (52) for circulating the coolant, the second coolant circuit (52) comprising a milk storage tank (3) configured for heat exchange between milk and the coolant; a chiller (4) comprising a refrigerant circuit (53) configured for heat exchange between a refrigerant and said coolant; a fluid control device (9, 10, 10') 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); controlling the chiller (4) to control the temperature of the coolant based on a first set temperature when the coolant is guided from the chiller (4) to the first coolant circuit (51) comprising the heat exchanger (2); and a control circuit (5) configured to control the chiller (4) to control the temperature of the coolant based on a second set temperature when the coolant is guided 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 are different, the first set temperature being higher than the freezing temperature of the milk but lower than 4°C, and the second set temperature being lower than the freezing temperature of the milk.

11. A computer program comprising instructions to cause a dual refrigeration system according to claim 10 to carry out the steps of the method according to any one of claims 1 to 9.

12. A computer readable medium storing the computer program of claim 11.

Images