Heat transfer principles

Two substances must have a different temperature in order to transfer heat. Heat always flows from the warmer substance to the colder. The greater difference, the faster it equalizes.

 All heat transfer in Dairies take place in the form of direct or indirect heating e.g. a Pasteuriser unit can have a small soldered PHE where steam goes direct in the water, the water gets hot and used indirectly in The pasteurizer unit to heat the milk to desired pasteurising temperature.

The same thing happens in milk cooler e.g. in the milk reception, the only difference is in the media — Ice water, not steam.