CHILLER UNIT This invention relates to improvements in or in relation to refrigeration systems and refers particularly, though not exclusively, to refrigeration systems where liquids have to be cooled and kept cool for a period of time in large storage tanks. In modern dairies milk is passed along a pipe through an initial cooling stage using plate coolers which can be cooled, for example, by water or air, and into a large storage tank or vat. These are of large capacities - quite often of the order of eight- or twelve-thousand litres. The vats are normally refrigerated so that the milk can be cooled to a low temperature such as 2-4°C so as to reduce bacteria in the milk from multiplying and to keep the milk in good condition until collected and taken to the appropriate plant. When milking commences, the entire refrigeration system in the vat is operating yet only a small amount of milk is being cooled. Also, the vat is quite often not filled but must have a refrigeration system adapted to cool all of the milk that comes in and thus there is a considerable excess in the cooling capacity for the vat. It is therefore the object of the present invention to provide a chiller unit for use in situations such as dairies, fruit juice processing plants, or any other place where a liquid must be cooled and then held in storage so that the liquid entering the vat is at the correct temperature and thus the vat merely needs to hold the liquid at its correct temperature.

With the above and other objects in mind the present invention provides a chiller for liquids, said chiller including an insulated tank having a coil mounted therein with said coil having an inlet and outlet for said liquid to be chilled, said tank being filled with a cooling medium and at least one cooling means located in said cooling medium, said at least one cooling means adapted to be operatively connected to a refrigeration system.

Preferably, there is also a holding tank adapted to receive said cooling medium when said coil is being cleaned or serviced.

In order that the invention may be fully understood there shall now be described by way of non-limitative example only a preferred construction of a chiller unit incorporating the principal preferred features of the present invention, the description being by way of example only and with reference to the accompanying illustrative drawing in which:-

Figure 1 is a side view in cross-section showing a schematic arrangement of the chiller unit according to the invention;

Figure 2 is a cross-sectional view of the lower section of the chiller unit shown in Figure 1 ;

Figure 3 is a cross-sectional view along and in the direction of arrows 3-3 of the chiller unit shown in Figure 2; and Figure 4 is a schematic representation of a dairy fitted with a chiller unit of the present invention.

In the drawings there is shown a chiller unit 1 which comprises an outer tank 10 in which is contained an inner tank 12. In the void between the outer tank 10 and the inner tank 12 is an insulating means 14 - preferably an expanded foam. Located within the inner tank 12 is a coil 16, preferably of stainless steel, adapted to have pass through it the liquid to be cooled. The coil 16 has an inlet 18 and an outlet 20, with the inlet 18 and outlet 20 passing through both the outer tank 10 and the inner tank 12. If the chiller unit 1 is to process a liquid for human consumption, the coil 16 must be of a food grade quality.

Also located within the inner tank 12 is a first cooling means 22 which in this particular instance are dimple plates and which are operatively connected to a refrigeration system 48 via an inlet 24 and an outlet 26, both of which again pass through the walls of the inner tank 12 and outer tank 10. The first cooling means 22 can lie within coil 16 or encircle coil 16 as shown. If

Jequired, a second cooling means 23 of similar construction to first cooling means 22 may be fitted. Again the dimple plates of second cooling means are operatively connected to a refrigeration system 48 via an inlet 25 and outlet 27. The inner tank 12 is filled with a cooling medium 28 which may be water, glycol, or any other appropriate cooling medium. Preferably the cooling medium 28 is a mixture of water with glycerine in the ratio of three parts glycerine to one hundred parts water. Advantageously the glycerine is food grade. It is preferred that an anti-algae solution be added at an appropriate concentration. In this way, upon the operation of the refrigeration system 48 the refrigerant passes through the dimple plates 22,23 to cool them to thus cool the cooling medium 28. This therefore lowers the temperature of the coil 16 so that liquid passing through coil 16 will be cooled. In this way the liquid passing through the outlet 20 will be at the correct temperature. It is preferable that there be a temperature sensing means 40 at the outlet 20 so that when the temperature of the liquid at outlet 20 has dropped sufficiently the refrigeration system (not shown) can be turned off and then cycled to ensure that the temperature of the liquid at outlet 20 is correct at all times.

Obviously when dealing with liquids which are foods, the coil 16 would have to be cleaned at least from time to time. This is normally done by passing hot water through the coil 16. In this particular instance, with the cooling medium quite cold, the hot water will cool very quickly and thus not be able to perform its function. Also, it will be removing much of the "cold" and cooling effect from the cooling medium and this is energy inefficient. Therefore, a pump 30 is located in the inner tank 12 (or external to it as illustrated) and is connected to a pipe 32 so that the cooling medium 28 can be pumped by the pump 30 through an outlet 42 in inner tank 12 via intake connection 44 and through pipe 32 and

into a holding tank 34. The holding tank 34 is located in an outer tank 35, with there also being an insulating medium 33 therebetween. The construction is similar to that of outer and inner tanks 10,12. The tank 34 can be located at any suitable location relative to the outer tank 10. As illustrated, it is above, with a frame 37 supporting them both. Once all of the cooling medium has been passed into the tank 34, a valve 36 is closed to prevent the return of the cooling medium 28 through the pipe 32 and pump 30. The hot water can then be passed through inlet 18, through the coil 16 and out through outlet 20 to thus clean the coil 16. When this operation has been concluded, a second valve 38 can be opened to allow the cooling medium to pass therethrough and into the inner tank 12, to thus re-fill the inner tank 12. In this way, if the holding tank 34 is located above the outer tank 10, gravitational force can be used to provide the appropriate fluid passage. At this time the valve 36 may also be opened to allow any cooling medium located in the pipe 32 to re-enter the tank 12.

Preferably tank 12 has a lid 46 so that access can be gained to the interior for necessary cleaning and/or servicing. As is shown in Figure 4, a dairy could incorporate a chiller unit 1 within the dairy to pre-chill milk before it enters the vat 2. A transfer pump 3 may be provided, as may a filter 4, and the usual plate cooler 5. In this way, the temperature of the milk entering the vat 2 from the chiller 1 will be at the required temperature (3.2°C) to thus reduce the refrigeration requirement and electricity load for vat 2.

Preferably, the pump 30 may also be used to fountain the cooling medium within the tank 12, or a separate pump may be provided. In the illustrated embodiment a manifold 50 is coupled to pump 30 through valve 36. A plurality of riser tubes 52 extend vertically from manifold 50. Riser tubes 52 have perforations for allowing cooling medium 28 to flow therethrough. In use, pump 30

will withdraw cooling medium 28 through outlet 42 and force it through manifold 50 where it issues through the perforations in riser tubes 52. It is preferred that riser tubes 52 be closed at their ends remote from manifold 50. Alternatively, a rotating paddle could also be provided to circulate cooling medium 28.

It is to be realised that the present invention may be suitable for use with any particular liquid such as, for example, milk, fruit juice, wine, grape juice, or any other liquid intended to be used for human or animal consumption. Tests have been carried out on three beverage coolers. Two were "ice bank" type coolers which were filled with "glycol" to give the best possible comparison of performance between them. The third, was in accordance with the present invention.

The protocol used involved running at the rate of 80 millilitres per second and measuring the temperature of the beverage at time 0, 30, 45 and 60 seconds. In suitable cases, the run time was extended as shown in the table. A beverage temperature of over 3.5°C is considered unsatisfactory, and testing was not continued far past this point. The results given in °C obtained from the three different units were as follows:-

Inlet temperature 14°C

Time (sec) 0 30 45 60 Comments

Concord (ice) 2.2 4.3 4.9 5.2 Average of 3 runs TempRite (ice) 5 7.2 8 8 Average of 2 runs

Current invention 1 .4 2.7 2.9 3.1 Average of 2 runs

Whilst there has been described in the foregoing description

a preferred construction of a chiller unit incorporating the principal features of the present invention, it will be understood by those

skilled in the technical field concerned that many variations or

modifications in details of design or construction may be made

without departing from the essential features of the invention.