Conduction and convection:

Conduction and convection both transfer heat but in their
own unique way firstly conduction requires a direct contact with the molecules
to allow heat transfer and conduction occurs not only in metals but also in
liquids as well. In comparison with convection this method of transferring heat
which takes place in all fluids which include the heat passing through the
liquids and gases. Another difference between conduction and convection is the
way the process differ from each other in conduction molecular collisions are
done in the substance which actually transfers the heat from one the heat
source throughout the whole material on the other hand convection relies on the
actual flow of the matter. This is a clear differentiation in the way the
actually how each methods carries out the transfer of heat in their own unique
way. And finally on of the major difference in conduction and convection are
the process and the way it is carried out in each of them and the examples of
objects they are carried out in. Firstly in conduction the process involves
transferring heat by heat the material at one end of a metal which will give
the particles energy which pass on the energy by direct contact with each other
eventually successfully passing the kinetic energy from one end to the other
however this can also take place in liquids because Liquids are also tightly
packed materials and so the particles are not really free to move about. This
puts them in the category of being in the process of conduction. However
conduction works best with metals which have a different molecular motion to
liquids. Solids have a vibrational motion which they are in a fixed position. In
comparison with conduction, convection relies on fluid currents to transfer
energy. In convection the material itself moves from one place to the other
however in conduction energy moves through the material. In comparison with
conduction convection relies on rotational motion which the molecules rotate in
and around the axis. This clearly shows the way their molecules behave during
the process. Unlike conduction convection relies heavily on bulk motion of a
fluid. For example, the flow of liquid water transports molecules or ions that
are dissolved in the water. the flow of air carries molecules presents in air,
including both concentrated species and dilute species. Convection does not
have surface properties because it does not have a surface.

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Convection and radiation:                                                                                                                

Radiation and convection transfer heat through different
methods. So one of the main differences between them is the way they transfer
heat. So firstly the difference is that convection relies on a medium to carry
the thermal energy from point a to point b. on the other hand radiation does
not require a medium to transfer its energy by. Another difference is that
radiation transfer heats using electromagnetic waves on the other hand.
Convection is a mechanism of heat transfer which involves a mass flow of
material. And one of the most interesting differences between the two is their
origin. Convection takes place because of thermal expansion of matter.
Radiation is a result of the motion of charges in materials due to kinetic
energy of the molecules. Temperature Dependence Convection results in a heat
flow rate that is approximately directly proportional to the temperature
difference. Radiation is effected in a heat flow level that is reliant on on
the difference between fourth powers of temperatures of the object and the
surroundings. Convection is the transfer of heat energy through the movement of
fluid particles. Hence, convection cannot take place in solids, since the solid
particles are not fluid. Therefore, convection only takes place in liquids and
gases. because of convective heat transfer between water molecules. In
comparison, radiation does not require any medium for heat transfer. Solar
radiation is an example of radiation or radiative heat transfer. Furthermore
the difference between the molecular motions of convection is rotational motion
molecule can rotate in and around the axis. 
and transitional motion in such kind of motion, molecules can move from
one place to another in same or different direction but always remains in same
axis. These type of molecular motions occur in convection however because radiation
does not have a medium it travels through. So the molecular motion is not known
unlike convection which totally depends on it. And also the bulk flow like
molecular motion of radiation because it does not depend on a state so mostly
convection mostly relies on it. Surface propertiesthermal radiation the surface
has many properties which include matte black surface which are good absorbers
and emitters of heat and the shiny silver surfaces are poor absorbers of heat
and good reflectors of heat. And convection does not have surface properties
because it does not have a surface.

Conduction and radiation:

Conduction and radiation are quite different from each other
from their surface of objects to the molecular motion. Each individual method
transfers heat in their own unique way. So firstly, let’s discuss the major
differentiation in their process and what it involves. Conduction is a process,
which involves the transfer of heat between objects through direct contact. On
the other hand, the process of radiation involves heat being
transmitted/transfer without any physical contact between objects. Another
difference between the two is in the process but two do with it at the
molecular form. Conduction can transfer heat in two states that is solids and
liquids but it does this more effectively in the state of solid. Therefore, the
process involves heat energy being transferred from one end of a material to
the other in this case the material that will be used is a metal. A metal
contains metal ions and free electrons. Ions are charged particles that are
made when metal atoms lose their electrons, which then become free electrons.
These ions are held closely together and they vibrate continually. The more the
heat an object receives the more kinetic energy these vibrations have. This kinetic energy is transferred from hot parts of
the metal to cooler parts by the free electrons. These move through the
structure of the metal, colliding with ions as they go. On the other hand the radiation
states that it does not require particles for heat transfer. Because radiation
does not require a medium to travel through such as a solid, liquid or gas. Radiation
uses electromagnetic waves to transfer heat. In addition, radiation is a result
of the motion of charges in materials due to kinetic energy of the molecules.
Like heat is transferred in metals by conduction. On the other hand, Solar
radiation is an example of radiation or radiative heat transfer. Another
difference between the two is the rate at which they transfer the heat. Radiation
is fastest way yet in transferring heat in comparison with conduction which is
a much slower process. But the rate of process of conduction can be manipulated
in the sense the more heat is given the faster the particles gain kinetic
energy and transfer heat. In heat radiation the law of refraction and reflection
does flow which can have its own advantages like transfer heat to places it
isn’t possible to do so in other methods this can reach every where through
reflection and refraction. For examples using giant/ small mirrors to reflect heat
onto another object. This is perfect example of transferring of heat by
radiation. Another  difference between
the two methods is their molecular motion. Conduction uses mostly the molecular
motion that is known as vibrational motion this type of motion  In this
type of motion, molecules can vibrate at their mean position. These motions are
very common in solid state. This is very well suited to the function of the
heat transfer that is by vibrations of particles and producing kinetic energy.
On the other hand unlike conduction the molecular motion of radiation is not
known. Because radiation does not require a medium to travel through. And so
does not involve particles but involves electromagnetic waves. And one final difference
between the two is surface properties:  
for e.g. thermal radiation the surface has many properties which include
matte black surface which are good absorbers and emitters of heat and the shiny
silver surfaces are poor absorbers of heat and good reflectors of heat. On the
other hand conduction has rough and smooth surface which effects the rate of
conduction.

Heat wastage in buildings can be minimised:

There are different and several ways in which heat loss can
be reduced. Fitting carpets and curtains is a simple way to reduce heat loss
also if possible to fit reflective foil in the walls and to fit a draught
excluder.

Another way that heat loss can be reduced through the
windows is by installing double glazed windows. They have air or vacuum between
them and therefore there will not be conduction or convection, this mean that
if the double glazing is made with air between the glass and convection will be
reduced and will leave little room for the air to move around as air is a very
poor conductor. Without double glazed windows there is a chance of bulk flow of
heat escaping through the glass as well as this the cold glass can turn the
heat to water vapour. The trapped air in the gap is an insulator, it does not
stop heat being conducted from the inner pane to the outer pane but it does
slow heat transfer by conduction down a lot. The air gap is too narrow to allow
the air to circulate easily. This therefore reduces the rate of heat transfer
by convection. The trapped air reduces the rate of heat loss through the window
by conduction and convection. The room in the house therefore stays warmer for
longer reducing heating costs. Heat radiates through air and glass, which it
does so some of it is reflected and some of it is absorbed. This percentage increases
as there is more glass but overall heat transfer by radiation is hardly changed
by double glazing a window, it is conduction and convection that change the
most. Molecular motion states that the double glazed widow will do a good job
to minimise heat loss. The reduction of conduction and convection due to the
fact that there are no molecules present in the double glazing which are the carrier
of heat energy from one end to another end. This prevents molecular motion
because there is not any molecules present at all in a vacuum so there for no
molecular motion takes place.

Heat loss in walls can be condensed by installing cavity
wall insulation. “This involves blowing insulation materials into the gaps that
are left between the brick and the inside wall.” Due to insulating materials
being bad conductors they will reduce heat loss by conduction and it also
prevents air circulating inside the cavity and therefore reduces heat loss by
convection. Without cavity insulation there is a risk of bulk flow of heat
escaping through gaps and holes in the walls. With double glazing and cavity
wall instillations the molecular motion of the heat convection around your home
therefore resulting to less waste of heat, keeping your home warmer and more
efficient.Cavity wall insulation slows down the rate at which it escapes,
keeping as much of it as possible inside your home for as long as possible. Cavity
wall insulation makes it much more difficult for heat to pass through your
walls by filling up the cavity with a material with lots of small air pockets
in it. These compartments are more efficient at dropping heat transfer by
convection than the big air cavity was. They make it impossible for large
convection currents to be set up. “They reduce what is known as your walls’ U
value – which is a measure of how quickly they lose heat.” The lower the U
value, the slower heat transfer – and the less energy you need to keep your
home warm.

Another way to prevent heat loss in houses is by installing
hot water tank jacket. This helps keep the tank which your hot water gets
stored after being heated by the boiler because if it’s poorly insulated then
the heat will get lost very quickly. This causes the boiler to use more energy
when reheating the water for any use.Is an insulator that covers the hot water
cylinder to prevent it from heat loss when it heats and boils up the water. It
may be a reason; it will cost a lot of money by boiling the water every time it
cools down because it is losing heat fast since it is not insulated. By putting
a jacket around the tank, the heat energy stays trapped inside longer before it
is lost. This reduces the processes of conduction, convection and radiation.By
adding these three important parts into a building we’re reducing the occurring
of these three processes. In addition, by reducing these processes we have
reduced the waste of heat in these buildings. The shiny surface of the jacket
reflects the radiation so the transfer of heat does not take place. And
prevents heat transfer by radiation.

References:

http://www.machinedesign.com/whats-difference-between/what-s-difference-between-conduction-convection-and-radiation

http://chemistry.tutorvista.com/physical-chemistry/molecular-motion.html

http://www.spaceflight.esa.int/impress/text/education/Heat%20Transfer/Conduction%2001.html

http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/heatingandcooling/heatingrev4.shtml

http://www.g9toengineering.com/resources/heattransfer.htm

https://www.comsol.com/multiphysics/what-is-convection

Difference Between Convection and Radiation

https://www.enotes.com/homework-help/what-state-matter-conduction-convection-take-place-707689

https://www.edinformatics.com/math_science/how_is_heat_transferred.htm

http://www.sciencedirect.com/science/article/pii/S1007570411002760

Difference Between Conduction, Convection and Radiation

Insulating your Hot Water Tank

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