Thermal Radiation Light Bulb

The example used to show how to model heat transfer in a recent webinar involved modeling the natural convection flow with heat in a light bulb.

Thermal radiation light bulb.

The sun is a huge thermal reactor about 93 million miles away in space and neither conduction nor convection can produce any of the energy that arrives to earth through the vacuum of space. Because incandescent and halogen bulbs create light through heat about 90 of the energy used is wasted to generate heat. Modeling a light bulb. That s written in stone.

In fact it is the light of day. To reduce the heat emitted by regular incandescent and halogen bulbs use a lower watt bulb like 60 watts instead of 100. Thermal radiation is electromagnetic radiation generated by the thermal motion of particles in matter. Thermal radiation is well known from light bulbs and from the sun for example.

Thermal radiation ranges in wavelength from the longest infrared rays through the visible light spectrum to the shortest ultraviolet rays. The total radiant heat energy emitted by a surface is proportional to the fourth power of its absolute temperature the stefan. Even if the temperature is not high enough to generate visible thermal radiation there may be strong infrared radiation which can be felt on the skin for example. The intensity and distribution of radiant energy within this range is governed by the temperature of the emitting surface.

The peak frequency in the spectrum of the thermal radiation emitted by an object. Again the choice of units depends on the situation. It was a particularly good problem to work through as modeling a light bulb requires taking all three forms of heat transfer into account as well as flow. The si units is the hertz but i prefer the gigahertz for peaks in the microwave bands like the cosmic microwave back ground and terahertz for peaks in the infrared.

Thermionic emission is the liberation of electrons from an electrode by virtue of its temperature releasing of energy supplied by heat this occurs because the thermal energy given to the charge carrier overcomes the work function of the material. In fact they manage to waste less than 10 of the power applied. The charge carriers can be electrons or ions and in older literature are sometimes referred to as thermions. All matter with a temperature greater than absolute zero emits thermal radiation.

F max. Heat energy transferred through radiation is as familiar as the light of day. Amazingly standard light bulbs manage to be extremely energy efficient despite the heat that they produce and despite the fact that their light comes from heated elements. Particle motion results in charge acceleration or dipole oscillation which produces electromagnetic radiation.

Therefore thermal radiation provides a mechanism for exchanging heat between objects.