The product is usually cooled indirectly (as shown in Fig. 2) - cooling system cools the air or liquid, known as secondary refrigerant, which in turn is used to cool the product. Product cooling medium (air or secondary refrigerant), provides the energy for evaporation of the coolant - Rule 2.

The refrigerant vapour is then compressed to high pressure. Its saturation temperature, then higher than the temperature of the surrounding air or water used for the removal of heat from the refrigerant. In consequence of the loss of heat converts a pair of back to liquid - Rule 3. Ambient air or water, as a consequence, to warm up. The fluid is returned to the evaporator of pressure-reducing devices. Two explanations should be, what to see, how the cooling system works.

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