Many specialized applications (ranging from advanced gas-turbine blades to medical devices and implants) require metal components that are coated with protective material layer. In a manufacturing plant for such coatings, infrared lamp is used for curing the coating on metal plates. The lamp provides uniform irradiation of which a flux of 1600 W/m2 is absorbed by the metal plate surface, which has an emissivity of 0.5 for the radiation at the temperature of the coating. Air is used to cool the plate, which is kept in an enclosed environment, and it enters the enclosure at 200C and leaves from the coating process at 300C. (a) If the convective heat transfer coefficient between the coated plate surface and cooling air is 15 W/ (m2 K), estimate the temperature of coating on plate surface.
(b) If the engineer who invented believes that the cure temperature (or surface temperature) of 500C provides a coating with better durability, estimate the infrared lamp irradiation necessary to attain the required average cure temperature for the process.
GIVEN
FIND
- Temperature of coating on plate surface
- Infrared lamp irradiation necessary to attain required cure temperature.
ASSUMPTIONS
- Steady state conditions prevail
- Other heat loss to surrounding is negligible
(a) The flux irradiated to the surface is dissipated by convection through convective heat transfer
through air and radiation from the surface. Thus
(b) If the surface temperature of 500C provides a coating with better durability, the irradiation
required on the surface for Ts=323 K is given by
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