Slides in this set
Thermal radiation is the transfer of heat by infra-red
waves, which are part of the electromagnetic
All objects emit heat radiation
The hotter an object, the more heat radiation it
Heat radiation passes through a vacuum, this is how
we get our heat from the sun.
The transfer of heat radiation does not involve
SURFACES AND RADIATION
Dark, matt surfaces are good absorbers of
radiation, so they will get hotter if left out in the
sun than a shiny white surface.
However they are also good emitters, and they
will lose heat quicker than a shiny white
Conduction is the transfer of heat through a substance ,
usually a solid, gases and liquids are poor conductors of
When one end of a metal is heated, then those end
particles gain kinetic energy and they vibrate each other
and gain more energy.
Metals also have delocalised (free) electrons, which
vibrate throughout the metal and pass on their energy.
Poor conductors are called insulators.
Good insulators have pockets of air to trap heat in, for
example air pockets in fibreglass.…read more
Convection occurs in fluids, that is liquids and
When a fluid is heated it expands and becomes
less dense, due to this lower density, it rises and
it is replaced by cooler fluid. This process
repeats and you get what are called convection
HEAT TRANSFER BY DESIGN
Heat transfer by conduction can be reduced by
Heat transfer by convection can be reduced by
preventing convection currents from forming,
for example trapping air in pockets.
Heat transfer by radiation can be reduced by
using light shiny surfaces.
The converse can be applied to maximise heat
loss to keep things cool.…read more