The DOST's Immersion Type Freezer

The DOST immersion freezer has a volume capacity of 1,000 liters and freezing capacity of 60 kilograms per hour for ice making – other food products assume different values. It has adjustable coolant temperature and dividers for small volumes.

How immersion freezing works? It is done by soaking the commodity in liquid coolant. Imagine a chest freezer filled with water. Open the door, submerge the food, close it and wait until frozen.

Why immersion freezing? It is more efficient than grocery freezer and air blast freezer. Transfer of heat from liquid to solid is faster than air to solid. It uses brine solution as coolant. Its temperature can go as low as -21ºC without freezing. At temperature of -18ºC the brine solution is still liquid while the soaked bag of water is hard solid.

Maybe it is not meant to perform quick freezing, freezing and preventing the expansion of water molecules.

I did a quick googling. Popular immersion freezers use liquid nitrogen as freezing medium. Its temperature is much lower than of brine’s. It boils at -196ºC and freezes at -210ºC. Immersion freezers with liquid nitrogen as coolant do a very efficient quick freezing that never allow water molecule expansion and preserve food structure. However, liquid nitrogen is more expensive and harder to handle. It boils on contact with other objects and creates thick vapors.

Suitable only for sealed products. Obviously not for making ice buko. May not be suitable for ice candy. All commodities meant for freezing should be well sealed to prevent even the smallest entry of brine. The type of polymer or container must be impermeable.

The DOST immersion freezer is a collaborative project of the Industrial Technology Development Institute, Metals industry Research and Development Center, and the Project Management Engineering and Design Service Office.

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