Heat Transfer
Infrared Energy
Definitions
Radiation
transfer of energy by way of electromagnetic waves
Conduction
transfer of heat from a warmer molecule to a cooler molecule
Convection
transfer of heat through a fluid (gas or liquid) from an area of higher
temperature to a an area of lower temperature
Thermal energy
total energy of a substance's particles due to their movement or vibration
Temperature
a measure of the average energy of motion of particles of a substance
image source:
http://www.geography.hunter.cuny.edu/~tbw/wc.notes/2.heating.earth.surface/mechanisms_heat_transfer.htm
A lamp with an incandescent bulb was used as a heat source.
The lamp emits light and long-wave radiation called infrared.
The beakers contain either sand, soil, gravel, or water. Each
beaker had a lamp. A starting temperature was recorded for
each material. The lamp was turned on for 10 minutes and then
turned off for 10 minutes. Temperatures were recorded at the
end of 10 minutes of heating and after 10 minutes of cooling.
Changes in thermal energy were measured using an electronic
temperature probe. White paper and black paper were included
in the experiment to study the effect of color on heat transfer.
Data
Analysis
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Heat energy was transferred from the lamp to the sand by radiation. Heat
spread through the sand by conduction. When the sand cooled, heat was
transferred into the air by conduction. Air moves up from the sand by
convection
Heat transfer is the same as in sand. The gravel retains thermal energy
because the gravel chunks are denser than sand.
Heat transfer is the same as in sand. Soil is darker than sand and
therefore absorbed more radiation. The soil particles were loose and
released the heat energy. The soil was also dry.
Heat transfer is the same as for sand, except that heat also circulates in
water by convection. Water has a high heat capacity because of the shape
of the water molecule.
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Heat is transferred to the paper from the lamp by radiation. Black paper
will absorb most of the light and convert it to infrared. Therefore, black
paper will be warmer than white paper.
Heat is transferred to the paper from the lamp by radiation. White paper
reflects most of the light energy and little is converted to infrared.
Therefore, white paper remains cooler than black paper.
Conclusions
Light colored materials will absorb less light and infrared energy than dark
colored materials and will be cooler by comparison. Dense materials will conduct
heat more readily than less dense materials. If this is true, then blacktop should
convert more solar energy into heat than light colored concrete even though both
materials are dense. Soil although dark should be cooler than either blacktop or
concrete. Areas near water may be cooler because of convection occurring over
water due to a temperature difference between a body of water and land.