A thermal processing apparatus includes a conveyor belt for supporting work products during thermal processing that moves along a spiral path moving in a first direction arranged as a first tiered stack and then moves along a spiral path in a second direction arranged as a second tiered stack. A circulation system induces gaseous thermal processing medium from the tiers of the first and second spiral conveyor belt stacks and forces the thermal processing medium through a heat exchanger and then back to the tiers of the spiral conveyor belt stacks. The first tiered stack is divided into a first processing zone and a second processing zone, and the second tiered stack is divided into a third processing zone and fourth processing zone. A source of thermal processing medium is directed at the first processing zone to thermally treat the work product in the first zone by enhanced heat transfer. Optionally, a source of thermal processing medium is directed at the fourth processing zone to complete the thermally treatment the work product.

Heating systems utilizing radio frequency (RF) energy and methods for using the same to rapidly and uniformly heat packaged articles moving through the system on one or more convey lines. These systems may be useful for a variety of processes, including the pasteurization or sterilization of packaged foodstuffs.

The conveyor belt (24) of an oven system and apparatus (20) is configured into ascending and descending spiral stacks (26) and (28) to define a central cylindrical channel (62). A pair of upper and lower fans (130) and (132) are positioned within the central channel (62) to circulate thermal processing fluid in upper and lower circuits vertically through the spiral stacks and also laterally toward the inlet of the fans (130) and (132) to set up upper and lower thermal processing zones in the spiral stacks and circulation routes for the cooking medium through the spiral stacks.

The conveyor belt (24) of an oven system and apparatus (20) is configured into ascending and descending spiral stacks (26) and (28) to define a central cylindrical channel (62). A pair of upper and lower fans (130) and (132) are positioned within the central channel (62) to circulate thermal processing fluid in upper and lower circuits vertically through the spiral stacks and also laterally toward the inlet of the fans (130) and (132) to set up upper and lower thermal processing zones in the spiral stacks and circulation routes for the cooking medium through the spiral stacks.