Convection

Heat is needed by the web to feed the evaporation of the ink solvents and to increase the temperature of the ink solids and web. Forced air dryer systems operate on the principle of convective heat transfer. As the web passes through the forced air dryer it gains heat from the air turbulence inside the dryer.

We can increase convective heat transfer rate in only three ways:

• Increase the convective heat transfer coefficient of the dryer.
• Increase the effective surface area of the web being acted upon by a dryer.
• Increase the temperature difference between the web and the dryer.

Other types of drying systems provide heat to the web by conductive heat transfer, infrared light radiation, microwave radio frequency radiation, or other principles. These forms of heat transfer are different from convective heat transfer.