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What are the 3 different types of heat transfer?

and i also need examples of each.

thanks ((:

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They aren't so much different types, the word modes is preferred. There are three modes of heat transfer.

Mode 1: conduction. Direct heat transfer through molecular/atomic collisions. The only mode of heat transfer which works through solids.

Mode 2: convection. Heat transfer by conduction in a fluid, enhanced by the flow of the fluid.

This flow can either be pre-existing and it is called forced convection, or it can be a buoyantly driven flow in a gravitational field and is called natural convection.

Mode 3: radiation. Heat transferred by electromagnetic waves, emitted by bodies based on their individual temperature and emissivity (how black the body is). Also absorbed and converted to heat by bodies if there is incident radiation on their surface (also dependent on the property emissivity).

A hot object has a net emission of radiation, a colder object has a net absorption of radiation.

Radiation heat transfer typically uses infrared rays to carry the energy, which is why you don't see it. Objects which are hot enough will emit visible light.

Emissivity can be thought of as a participation in radiation fraction. Black bodies fully participate, "white" bodies do not participate should they exist. Gray bodies partially participate, and the same fraction of participation at each "color".


Examples:

Mode 1: your frying pan conducts heat through its iron body from the source of heat to the food.

Mode 2 forced: a computer fan is used to remove heat dissipated by the computer chips.

Mode 2 natural: during the daytime, air above hotter land rises, and is displaced by cold air over the nearby lake. The hot air eventually cools and falls over the lake. You notice this because of the daytime wind direction, inland.

When night falls, the water is warmer than the land, and the opposite wind pattern occurs, out to the lake.

Mode 3: when you are on the beach on a hot day in the tropical regions, the air is comfortable, but the sand burns your feet. This is because the sand absorbs the sun's incident light and converts it to heat. The ambient air cools it off by convection, but it still stabilizes at a temperature uncomfortable to your feet.