21-09-2013, 12:41 PM
Radiation Heat Transfer
[attachment=58171]
Introduction
Radiation is a photon emission that occurs when electrons change orbit. Thermal radiation occurs
when the excitation is caused by heating.
The following figure shows the relatively narrow band occupied by thermal radiation.
An even narrower band inside the thermal radiation spectrum is denoted as the visible spectrum,
that is the thermal radiation that can be seen by the human eye. The visible spectrum occupies
roughly 0.4 − 0.7 μm. Thermal radiation is mostly in the infrared range. As objects heat
up, their energy level increases, their frequency, ν, increases and the wavelength of the emitted
radiation decreases. That is why objects first become red when heated and eventually turn white
upon further heating.
[attachment=58171]
Introduction
Radiation is a photon emission that occurs when electrons change orbit. Thermal radiation occurs
when the excitation is caused by heating.
The following figure shows the relatively narrow band occupied by thermal radiation.
An even narrower band inside the thermal radiation spectrum is denoted as the visible spectrum,
that is the thermal radiation that can be seen by the human eye. The visible spectrum occupies
roughly 0.4 − 0.7 μm. Thermal radiation is mostly in the infrared range. As objects heat
up, their energy level increases, their frequency, ν, increases and the wavelength of the emitted
radiation decreases. That is why objects first become red when heated and eventually turn white
upon further heating.