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1. Heat Transfer. Three Modes of Heat Transfer
There are three modes of heat transfer: conduction, convection, and radiation (fig.

1.1). Any energy exchange between bodies occurs through one of these modes or a
combination of them. Conduction is the transfer of heat through solids or stationery

fluids. Convection uses the movement of fluids to transfer heat. Radiation does not
require a medium for transferring heat; this mode uses the electromagnetic radiation

emitted by an object for exchanging heat.

Three modes of heat transfer:

- thermal conduction;

- thermal convection;

- thermal radiation.

Figure 1 – Conduction, convection and radiation heat transfer modes

1.1 Thermal conduction
Conduction is a heat transfer through solids or stationery fluids. When you touch a

hot object, the heat you feel is transferred through your skin by conduction. If you put
one end of a metal rod over a fire, that end will absorb the energy from the flame

(fig.2). Two mechanisms explain how heat is transferred by conduction: lattice vibration
and particle collision. Conduction through solids occurs by a combination of the two

mechanisms; heat is conducted through stationery fluids primarily by molecular

collisions.

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