Abstract: An air treatment plant for food is closed with the exception of an inlet and an outlet opening (3). In the plant, a pressure increase needed for circulating the treatment air tends to produce an air flow in one direction (29) through an inlet or outlet tunnel (20) communicating with the inlet or the outlet opening. The tunnel (20) has an upper wall (21) in which are arranged nozzles (22) directed substantially opposite to said direction (29), and a lower wall (23) formed with openings (24) for evacuating the excess air in the tunnel (20) produced by air jets (30) generated by a fan (27) and emanating from nozzles (22). A method for reducing the air flow in the inlet or outlet tunnel thus comprises the steps of directing a plurality of air jets (30) from the upper boundary surface (21) of the tunnel (20) substantially opposite to said direction (29), and evacuating from the tunnel the excess air produced by the air jets through openings (24) in the lower boundary surface (23) of the tunnel.

Abstract: An air treatment plant comprises a housing (1); a conveyor (4) adapted to feed food to be processed through an inlet opening (2) in the housing, to and through an air treatment area, and to feed the processed food from this area to and through an outlet opening (3) in the housing; a heat exchanger; and a circulation fan for generating a circulating air flow through the heat exchanger, the air treatment area, and the circulation fan in succession. A pressure regulating fan (25) is connected to a chamber (33) adjacent to one of the inlet and outlet openings (2, 3) for generating a pressure difference across that opening substantially equal to that across the other opening, thus minimizing the air exchange between the interior and the exterior of the housing (1). The conveyor (4) inwardly of this one opening passes a tunnel with at least two air curtain ducts which are directed substantially transversely of the conveyor path and through which some of the circulating air flows.

Abstract: An apparatus for air-treatment of products includes an endless foraminous conveyor belt for the products which is adapted within the space for the air-treatment to follow at least one path extending helically in several turns, said path for the foraminous conveyor belt being defined by an inner cylinder and an outer cylinder and the air being disposed to flow through the passage situated between the cylinders from one end to the other end of the passage. According to the invention the air is also disposed to be supplied to the passage between the cylinders from the inner cylinder through perforations therein, the size of the perforations and/or the interspace therebetween being so chosen that the air supply from the inner cylinder continuously varies in the longitudinal direction thereof.