Quick freezing

Where irregular shape of the product, the only way to extract the heat by means of cold fluid around him. Air is the obvious choice - it is economical, hygienic and relatively does not cause corrosion of the equipment. Air temperature will be around -40C and air velocity over the product will be high to get a good heat transfer. Air circulation around the stacked product in a cold room is used for batch processes. This requires a good air distribution and optimal correlation exists between a reduction in the freezing time and increase of the power required to drive fans, in order to increase the speed of the supply air.

Discrete parts of the product, such as peas, sliced carrots, beans and details of this size, can be passed on perforated tape. This can be a fluidized bed, where cold air enters through openings for cooling the product and campaign to prevent sticking or to a belt or similar works. Flat pieces of product, such as fish fillets will undergo a change in shape in the free air shock wave and better on flat moving belt. Here, some of the heat goes straight into the cold air and thermal conductivity to the waist, which is usually made of stainless steel. The tunnel can be designed to absorb much less fan power that increases the efficiency, because the fans are located in the cooled space and heat produced by their motors adds the cooling load.

Linear tunnels have a limit on the length of the belt, necessary for the achievement of cooling required time and place. Conveyors wound in a spiral shape, and contained in a cold room with air coil offer a more compact arrangement (see Fig. 14.1 and 14.2). Spiral freezers are very good for the larger entities, such as the baths of the ice cream that take a long time to harden and which has a direct pipeline would be too long for convenience.

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