Heat Transfer-class blog 1

Ever wondered how the Earth is heated? The Earth is heated through conduction, convection, and radiation.

Conduction is the direct transfer of heat energy from one substance to another. When the air above the Earth's surface and the warm ground meet, the air becomes warmer. In other words, the ground is warmer than the air above the ground. And, yet, soil, water, and air are not very good conductors of heat. Thus, conduction has a very small role in heating the Earth's surface.

Convection is the the transfer of heat energy in a fluid which is a gas or a liquid. So, air is a fluid. As air near the surface of the Earth is heated, the air loses density and it rises. The cooler and denser air that is further above the Earth's surface sinks. While the air is sinking, it heats up and begins to rise again. Through this rising and sinking process come the convection currents. These currents are caused by the unequal heating of the Earth's atmosphere. Most heat energy is transferred by convection currents.

Radiation is the transfer of heat energy through a vacuum, empty space. In other words, heat energy transferred through the means of radiation does not require a solid or a fluid. The heat energy from the sun reaches the sun through radiation.

Heat transfer is very interesting to learn about because people realize how heat actually comes to us. Without these processes, we would not have any heat to keep us warm, and we would always stay cold. In addition, heat transfer cannot be seen, so learning about it is essential to understanding how the Earth works.

Some interesting facts:

1. Heat is transferred by conduction when atoms next to each other vibrate against each other, or when electrons travel from one atom to another. This process is more common in solids because the molecules are closer together, so they vibrate against each other more. Because the molecules in fluids are further apart, conduction very rarely occurs in them.

SOURCE: Wikipedia
Hyperlink: http://en.wikipedia.org/wiki/Heat_transfer

2. Examples of Heat Transfer-
CONDUCTION- Our hand gets warm when we hold the handle of a pan that is on the stove because the heat goes from the handle (one substance) to our hand (the other substance).
CONVECTION- In our homes, we use furnaces to produce heat to keep us warm. The furnace heats the air in our home, and this air is then pushed throughout our home. The movement of the air is an example of convection.
RADIATION- As mentioned above, the sun's heat comes to the Earth in the form of radiation. Because the sun is extremely hot, the Earth can absorb the sun's energy.

SOURCE: Ezine @rticles
Hyperlink: http://ezinearticles.com/?Heat-Transfer-Facts-You-Should-Know-To
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PICTURE from: (click on image to enlarge) http://www.williams.edu/resources/sustainability/green_buildings/
images/convection_conduction_radiation.gif