Milk Chillers are basically designed with two concepts. One which is called bulk milk chiller where the raw milk will be cooled in a semi cylindrical stainless steel tank with direct expansion refrigeration system. This machine will suit the village co-operative societies and collection centers. The other one is online milk chiller is an indirect secondary refrigeration system, in which the raw milk collected from the collection centers will be handled by the secondary refrigeration system.
The milk cooled at +2˚C online process with plate type heat exchanger. The evaporators are designed with SS 304, 316 L Grade plate type heat exchangers. Milk chillers will maintain the temperature range from +2˚ C To + 30˚ C ˚ ± 1˚ C, capacity from 3000 Kcal/Hr to 150000 Kcal/Hr, 30 LPM to 650 LPM with different flow capacity. If the water temperature differentials between inlet and outlet are high, then a large external water tank would be used to store the cold water. In this case the chilled water is not going directly from the chiller to the application, but goes to the external water tank which acts as a sort of temperature buffer or (cold bank) the cold water tank is much larger than internal water tank. The cold water goes from the external tank to the application and the return hot water from the application goes back to the external tank, not to the chiller. Advantages of these method is large amount of milk can be cooled or processed with lower capacity machines and also process time will be shorter. The same application will be followed for liquid like wine, soft drinks and fruit juices. Milk Chillers are ozone friendly, packed with features and designed for many years of trouble free operation.
The above said cooling methods work well for smaller dairies that holds around 40 cows, but for large numbers of animals a better system was needed to rapidly cool the incoming warm milk. This is usually done using a device known as a Plate Chillers, which is a heat exchanger. Alternating stainless steel plates cause the milk to flow in a thin sheet across the plates, while cold water is circulated in a thin sheet on the other side of the plates. Plate Chillers flatten out the milk flow which permits quick and even cooling of the milk, compared to a round tube where the center core does not cool as rapidly as the walls.
But the milk still is not as cold as it needs to be, so the milk storage tank is still used to do further cooling, to bring the milk down to 40 degrees. But with the development of high-power 3-phase electrical service, ice bank chillers are typically no longer used. Instead the milk storage tank is a direct cooling system with cooling coils embedded in the walls of the tank, that quickly pull the heat out and dump it across a large array of possibly several different high horsepower compressors and condensing units. Once the milk has achieved 40 °F (4 °C) after milking is finished, it is ready for storage or transport. One or two cooling units to run occasionally is enough to maintain the correct temperature.