Tube ice is formed on the inner surface of vertical tubes and is produced in the form of small hollow tube ice machine of about 50 x 50 mm with a wall thickness of 10 to 12 mm. The tube ice plant arrangement is similar to a shell and tube condenser with the water on the inside of the tubes and the refrigerant (Ammonia) filling the space between the tubes. The machine is operated automatically on a time cycle and the tubes of ice are released by a hot gas defrost process. As the ice drops from the tubes a cutter chops the ice into suitable lengths, nominally 50 mm, but this is adjustable. Transport of the ice to the storage area is usually automatic, thus, as in the flake ice plant, the harvesting and storage operations require no manual effort or operator attendance.
The discharge system from the plant incorporates an ice crusher which can be adjusted to give an ice particle size to suit the customer’s requirement. The usual operating temperature of this type of plant is -8°C to -10°C. The ice will not always be sub cooled on entering the store but it is usually possible to maintain the store at -5°C since the particle size and shape allow the ice to be readily broken up for discharge.
The production capacity of the tube ice machine is a function of the evaporating temperature, the temperature of the feed water and the length of the freezing cycle. Based on the price of electric power and the purpose for which the ice is to be used, the refrigeration capacity employed and the length of the freezing cycle can be chosen within very wide limits so as to achieve the most economical operation.