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Infrared and Its Application For Drying Coatings On Webs
AIMCAL FALL TECHNICAL CONFERENCE2005
By: Bob NarangRadiant Energy Systems, Inc.
www.radiantenergy.com
Water or solvent based wet coatings applied on webs,are generally dried using three technologies:
1. Convection – such as a hot airimpingement or flotation dryer
2. Conduction –oil or steam heated drums
Heated Drum
Web Path
3. Infrared or Radiant Heating
IR Emitter
Web Path
Electric/Gas Infrared Heating System
Typical Conduction Heating System
Exhaust Air Plenum
Web Path
Recirc/ Exhaust
Heated Supply Air
Direct Impingement Convection Dryer
•• Theory of InfraredTheory of Infrared
•• Different types of infrared heatersDifferent types of infrared heaters
•• ApplicationsApplications
•• Advantages and LimitationsAdvantages and Limitations
•• AcknowledgementsAcknowledgements
Infrared Drying
Theory of InfraredTheory of Infrared
Electromagnetic Spectrum showing varioustypes of energy based on wavelength
Infrared SpectrumInfrared Spectrum
The Infrared spectrum can beThe Infrared spectrum can bedivided into three divided into three
categories:categories:1. Short Wave Length2. Medium Wave Length3. Long Wave Length
3 Basic Laws of Radiation3 Basic Laws of RadiationWienWien’’s Laws Law
The peak wave length of The peak wave length of emission of an infrared heater emission of an infrared heater can be calculated by Wiencan be calculated by Wien’’s Laws Law
λ = C/T
λ – wavelength in microns
C - Constant 2898
T - Source temperature (ºK)
Stefan Boltzman LawStefan Boltzman Law
W = kTW = kT44
W – Emitted Power
k - Constant
T – Source temperature (°K)
PlanckPlanck’’s Laws Law
Spectral Characteristics of InfraredSpectral Characteristics of Infrared
-- Absorbed by the object (A)Absorbed by the object (A)
-- Reflected by the object (R) Reflected by the object (R)
-- Transmitted through the Transmitted through the object (T) object (T)
A + R + T = 100% of A + R + T = 100% of energy received.energy received.
Absorption Curves for Different ProductsAbsorption Curves for Different Products
Types of HeatersTypes of Heaters
Short Wavelength Quartz Tube Short Wavelength Quartz Tube Emitter (TEmitter (T--3 lamp)3 lamp)
Medium Wavelength Quartz Tube Emitters
Medium Wavelength Stamped Foil Type Heaters
Types of HeatersTypes of Heaters
Long Wavelength Infrared Long Wavelength Infrared HeatersHeaters
Gas Fired Infrared Heaters
ApplicationsApplications
Infrared Air & Hot Air Dryeron a Coating Line
Infrared Air Pre-dryer
Advantages of Infrared DryersAdvantages of Infrared Dryers
§§ High efficiency conversion of electrical energy into heat for High efficiency conversion of electrical energy into heat for electrical IRelectrical IR
§§ Higher rate of heat transferHigher rate of heat transfer§§ Floor space savings due to smaller sizeFloor space savings due to smaller size§§ Heats only the object without heating the surroundingsHeats only the object without heating the surroundings§§ Easy to zone for uniform heating of the productEasy to zone for uniform heating of the product§§ Faster response to changing process conditionsFaster response to changing process conditions§§ Quick start up and shut downQuick start up and shut down§§ Easy to have cut off zones for narrow widthsEasy to have cut off zones for narrow widths§§ Ease of controlEase of control§§ Lower capital and installation cost Lower capital and installation cost §§ Can be easily be added to existing conventional dryers to Can be easily be added to existing conventional dryers to
increase line speedincrease line speed§§ Infrared Air dryers suitable for solvent based coatingsInfrared Air dryers suitable for solvent based coatings
Limitations of Infrared DryersLimitations of Infrared Dryers
§§ Some coatings may not be able to take advantage Some coatings may not be able to take advantage of of higher rates of heat transfer and may skin and higher rates of heat transfer and may skin and blisterblister
§§ Difficult to work with temperature sensitive Difficult to work with temperature sensitive substrates substrates
§§ Scaling up of the heaters is not always Scaling up of the heaters is not always straightforwardstraightforward
§§ Since IR is basically a surface phenomenon, Since IR is basically a surface phenomenon, harder to harder to dry heavier coatingsdry heavier coatings
§§ Almost essential to run trials in lab or on the pilot Almost essential to run trials in lab or on the pilot line toline to
confirm designconfirm design
AcknowledgementsAcknowledgements
§§ Infrared Process Heating Handbook by Industrial Infrared Process Heating Handbook by Industrial Heating Equipment AssociationHeating Equipment Association
§§ Handbook of Industrial Drying by Arun MujumdarHandbook of Industrial Drying by Arun Mujumdar
§§ Watlow IR HandbookWatlow IR Handbook
§§ Phillips Lighting HandbookPhillips Lighting Handbook
§§ Litex Infrared Lamps Litex Infrared Lamps
§§ Electric Process Heating by Maurice OrfeuilElectric Process Heating by Maurice Orfeuil
§§ Hydro QuebecHydro Quebec
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