Principles air would go in its place which

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Principles of Conduction, Convection
and Radiation

is when thermal energy which is transferred by direct collision or contact that
occurs between the particles. The types of conductive heat energy are molecular
motion and particle collision. Particle collision usually happens in fluids but
on the other hand molecular motion occurs in solids. Conduction can occur in
all states like liquids, solids and gases but is at its best in solids and
liquids this is because they have a higher density. Some of the mediums are
much better conductors then others. The good conductors of electricity are
usually good conductors of thermal energy as well like in metals. Particle
collisions happen in metals because they have free electrons. The process
occurs as particles gain thermal energy and as they gain this energy they will
also gain kinetic energy which causes them to vibrate more frequently. An
example of industry application of where conduction is used is in double-
glazing windows. In double- glazing windows has gas or vacuum which is found in
between the two glass slides reduces heat transfer which happens through
conduction because heat conducts poorly in gases and not in vacuums  the fact that conduction needs a medium and
it also reduces heat loss through radiation. Another thing is that solar energy
can enter the window because of the fact its short – wave radiation can
penetrate the glass. The wavelengths degenerate into long wave radiation in which
are in the inside these have a much higher chance to be reflected.


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convection is the process of which the transfers of energy by the actual
movement of the particles in fluids like liquids and gases. This cannot occur
in solids because of the fact that the particles inside solids are static. In
fluids there are areas in which gain thermal energy, they get lower in density
which makes it rise and makes the colder air would go in its place which
happens because of pressure gradient this is what causes the circulatory
currents to form. In industries an example where convection is used is in
radiators. Radiators are used to heat up rooms and the way they do this is by
radiators heating up the surroundings air this causes it to rise and causes a
pressure gradient which causes cool air to come and replace it and as the air
circulates it loses heat to the surroundings this warms up the house. Also bulk
motion is represented as the mass transfer motion in the fluids flow as opposed
to thermal diffusion. The currents are formed from buoyancy a force which is
caused by pressure gradients which is also caused by temperature gradient. When
this happens it causes the particles close to be grabbed by the current and
make it flow in the same direction with a similar velocity. In diffusion, the
velocity of each particle varies instantly does this randomly.


Radiation is
a process which happens through the transfer of energy which happens through
electromagnetic waves like infrared and visible light. Electromagnetic radiation
comes from when molecular vibration rises. The transfer of energy which happens
through this way does not need a medium due to the fact that the electromagnetic
waves are able to travel through a vacuum. There are many things that affect
heat radiation one of them being colour and origination. An example is a colour
like black which absorbs majority of wavelengths from visible light which means
that it heats up much quicker and the opposite of this are things which are
rubbish conductors of heat radiation are white and shiny surfaces. The
electromagnetic waves which hit the surface perpendicularly this would have a
higher chance of it turning into heat and would be absorbed rather than being
reflected. The fourth power of absolute temperature has another effect on this
because of the fact that a higher temperature would mean that more heat
radiation is emitted. An example of an industry application of thermal
radiation is home insulation. The fact that white surfaces usually reflect
radiation which is why walls and roofs can be painted white. Any thermal
radiation which is travelling to the outside has a higher chance of being
reflected back into the room this would reduce the heat loss. Another thing is
that radiators should be painted black as it allows them to emit radiation at a
much quicker rate but radiators are normally painted
white as in favour of aesthetics.

Categories: Industry


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