Mechanical Airflow Systems
Mechanical systems of cooling are numerous and come in a variety of temperatures, sizes, and construction materials. Three of the main types of mechanical systems are airflow freezers, brine freezers, and contact freezers. Airflow systems are defined by the type of cabinet, air flow, and the refrigerant used. Ammonia or hydrocarbons are pumped to the evaporator. Air is blown past the fans through fins, inside the tubing, the refrigerant boils off, and absorbs heat from the recirculating air. These systems must have defrost cycles if product is not packaged
Tunnel System – straight, continuous belt carrying product
- High velocity cold air via evaporator/fan units
- Airflow can be horizontal or vertical
- Take up more floor space than spiral
- Mechanically simpler, and less focus on maintenance and adjustment
- Small items short freezing times
Blast Freezer- batch freezing loaded on trolleys and wheeled into a cabinet
- Also called batch continuous systems, pallet placed product is moved row by row
- Circulated air is blown through above a false ceiling, over pallets uniformly
- Large products with long freeze times
Spiral Freezers- product enters freezer on belt with spiral motion through cube shaped cabinet
- Continuous feed, well controlled, very low air temperatures
- Occupy small amount of floor space
- Air flow is horizontal, vertical or combination of both
- Belt speed and loading density can be controlled
