Stationary Tunnel Freezer – Chilled Air
Industry: Fruit and Vegetables (NAICS 3114) Meat (NAICS 3116)
Process Brief: Products are frozen by putting them in chilled rooms in batch or continuous processes
Energy source: Electricity/ some Natural Gas
Energy Intensity: 250-1,700 Btu/lb of product
Tunnel freezers are used to freeze a wide variety of products. Most designs are basically an insulated room that is cooled by mechanical (electricity) or thermal (natural gas) chilling system. Air is circulated within the room to facilitate even cooling and air blast techniques may be used. In batch systems, the tunnel freezer has doors and pallets or trays of product are loaded and unloaded. A continuous system the tunnel freezer may incorporate an air curtain or other device to keep in the cold air. Consistent and even loading of the trays is essential to ensure even cooling.
Heat transfer rates are similar to air blast chillers and most products, such as blanched vegetables, can be frozen in less than 10 minutes, although the product may be piled 1-2 inches deep on the trays.