Nozzle arrangement in airborne web-drying and method for improving heat transfer in airborne web-drying

A method for for drying a coated fibre web comprising the steps of:

• passing a coated fibre web, passing from upstream to downstream between a plurality of first nozzle assemblies positioned on a first side of the web and extending across the web, the first nozzle assemblies defining first discharge passages therebetween which extend across the web, the first discharge passages for wet discharge air, and a plurality of second nozzle assemblies positioned on a second side opposite the first side of the web and extending across the web, the second nozzle assemblies defining second discharge passages therebetween for wet discharge air, the first nozzle assemblies and the second nozzle assemblies positioned so that each first discharge passage is opposite a second nozzle assembly, and each second discharge passage is opposite a first nozzle assembly;
• wherein each first nozzle assembly and each second nozzle assembly comprises:
• at least one overpressure nozzle extending across the web and having an upstream side and a downstream side, the overpressure nozzle having a first upstream nozzle slot extending across the web and a second downstream nozzle slot, which blow drying air jets obliquely against each other;
• and
• at least one direct impingement nozzle extending across the web, having a plurality of nozzle slots or nozzle orifices which blow drying air mainly perpendicularly against the web;
• and
• discharging wet air formed by the drying air jets of the overpressure nozzle and the drying air of the direct impingement nozzle away from the web through the first and second discharge passages.

A nozzle arrangement in an airborne web-drying apparatus for drying a coated fibre web, wherein the web has a travel direction which defines an upstream direction and a downstream direction, comprising:

• a plurality of first nozzle assemblies positioned on a first side of the web and extending across the web, the first nozzle assemblies defining first discharge passages therebetween which extend across the web, the first discharge passages for wet discharge air;
• a plurality of second nozzle assemblies positioned on a second side opposite the first side of the web and extending across the web, the second nozzle assemblies defining second discharge passages therebetween for wet discharge air, the first nozzle assemblies and the second nozzle assemblies positioned so that each first discharge passage is opposite a second nozzle assembly, and each second discharge passage is opposite a first nozzle assembly;
• wherein each first nozzle assembly and each second nozzle assembly comprises:
• at least one overpressure nozzle extending across the web, the at least one, overpressure nozzle having a first upstream a means for blowing air extending across the web and a second downstream means for blowing air extending across the web, arranged to blow drying air jets obliquely against each other;
• and
• at least one direct impingement nozzle extending across the web and having means for blowing drying air mainly perpendicularly against the web.