They are designed to bake a vast variety of products in pans or directly on the hearth. Tunnel ovens are divided into two broad groups, direct gas fired tunnel and indirect gas fired tunnel.
Direct gas fired tunnel ovens use air turbulence to achieve a uniform bake with strong product side walls in a shorter amount of time. The bake chamber’s temperature is determined by multiple thermocouple sensors that also provide zoned temperature controls. This feature allows for complete flexibility, precision and accuracy. In addition, individually controlled ribbon burners are located above and below the hearth for even heat distribution.
Finally, the hearth is generally made of stone, steel or tight or open mesh. A mesh hearth allows for air circulation and uniform patterning on the product underside. Indirect gas fired tunnel ovens instead operate using gas, propane or oil burners. These burners fire into a combustion chamber that supplies the radiant heat system contained within the bake chamber, which keeps combustion products outside the bake chamber and allows products to instead bake inside heated ambient air.
Indirect tunnel ovens, like direct tunnel ovens, may have a mesh hearth that allows for air circulation and uniform bottom baking as the products move through on the conveyor. Manufacturers may include full lateral adjustments in upper and lower zones for bake control, or may even offer steam zones.
Other types of tunnel ovens include air impingement, infrared, radiant-tube, thermal-oil, electric, dual-fuel and hybrid. Manufacturers also commonly offer custom design services to meet your specifications. They do so by calculating capacity and dimensions based on your requirements, resources and size conditions of your facilities.
They make sure to build you the right baking surface and select humidity and temperature control settings that will optimize your application’s color, surface temperature and moisture content. The right tunnel ovens will help your application succeed with better quality products, increased speed of baking and drying processes and lower operating costs.