Infrared float bar
View Patent ↗Infrared air float bar for use in floating and drying a continuous planar web of a material in a dryer. Direct radiated or reflected infrared electromagnetic energy from an infrared light source in a removable channel assembly accelerates drying, or evaporation of solvents, or curing of web material passing in proximity to the bar, either by infrared electromagnetic energy, or in combination with convention airflow. The infrared source is cooled by pressurized air passing through an interior portion of the removable air bar channel assembly, and the air is further conducted into fluid contact with the web in an air gap between the emitter and web to promote convective heat transfer and to contribute to the air pressure field supporting web flotation. The removable channel assembly is configured for replacement of the infrared emitter and to allow the setting of the pressurized cooling air flow to the optimum level.
1. A method of regulating drying of a web in a dryer by combined convective and radiative heat transfer, said web entering said dryer with wet areas alongside dry areas of the web, said method comprising providing in said dryer a plurality of air flotation bars that impinge air on said web and create a pressure pad, said air flotation bars having an infrared light source for applying an infrared heat flux to said pressure pad and a reflector for reflecting said infrared heat emitted by said infrared light source, and sensing air temperature of the air responsible for said convective heat transfer and regulating said air temperature in response to said sensing to a temperature effective for heating said wet areas while cooling at least a portion of said dry areas of the web prior to reaching the exit of said dryer such that the convective heat transfer cools said dry areas of said web while alongside wet areas are heated and said radiative heat transfer heats both said wet and dry areas of said web.
2. The method of claim 1 , wherein at least one of said infrared light sources comprises a medium wave carbon emitter, and wherein the heat flux of said emitter is in a range of 100 to 200 watts per inch.
3. The method of claim 1 , wherein at least one of said infrared light sources comprises a near IR emitter, and wherein the heat flux of said emitter is in a range of 200 to 400 watts per inch.
4. The method of claim 1 , wherein said plurality of air flotation bars provide heat convection heat transfer coefficient in the range of 10 to 40 BTU/hr-ft 2 -F.
5. The method of claim 1 , wherein at least one of said plurality of air flotation bars has an air flotation bar slot jet velocity in a range of from about 5000 to about 16000 feet per minute.
6. The method of claim 1 , wherein said dryer has an exhaust rate and wherein supply air is supplied to said air flotation bars, and wherein the air temperature in said dryer is controlled by regulating the exhaust rate of air in said dryer to from 5 to 30% of the supply air to said air flotation bars.
7. The method of claim 1 , wherein air temperature in said dryer is controlled by regulating power supplied to at least one of said infrared light sources.
8. The method of claim 1 , wherein supply air is delivered to said air flotation bars, said method further comprising passing from 5 to 40% of the total air supply delivered to said air flotation bars through an air distributor into uniform fluid contact with said infrared light source.
9. The method of claim 8 , wherein from 7 to 15% of said total air supply is delivered to said air flotation bars.
10. The method of claim 1 , wherein said web comprises ink printed on it thereby defining a web ink coverage portion and a web portion not covered by ink, and wherein said ink coverage portion of said web is less than said web portion not covered by ink.
11. The method of claim 10 , wherein said web ink coverage portion is the portion of said web heated by said radiative heat transfer, and said web portion not covered by ink is said portion of said web cooled by said convective heat transfer.