Infrared Heat Vs. Convection
Infrared radiation and convection are two common forms of heat transfer. Infrared radiation is a form of invisible light--or electromagnetic radiation--that's emitted by objects cooler than the sun, which emits in the higher-energy, visible spectrum. Convection is movement of heat contained in fluid.
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One Can Lead to the Other
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An object can heat nearby air through conduction (contact) and by infrared radiation. Then, with increased kinetic energy from the warmth, the air can rise above cooler air around it.
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Difference in Directionality
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Infrared radiation goes in all directions, while convection tends to be upward. The reason for this upward movement is that warmer gas or liquid particles have greater kinetic energy than their surroundings, and can fight gravity to propel themselves to a higher altitude.
Need for a Medium
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Radiation differs from convection in that it does need a medium through which to transfer, while convection uses a fluid, either liquid or gas, to convey its heat content. A rocket in space cools by radiation, not convection.
Difference in Transfer Rates
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The rate of heat transfer is generally much faster by convection than by infrared radiation.
An Example
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When convection is obstructed, heat content can build quickly. That is the basis of the greenhouse. Sunlight warms the floor, but the roof blocks cooling by convection. Infrared radiation is emitted out the glass, but at a slow rate in comparison, so the greenhouse heats up--even in winter.
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References
- Photo Credit Image by Flickr.com, courtesy of cassandra lavalle
