Let’s start with
questions like what is the heat? How heat is formed?
Heat is defined as a
form of energy, so we can utilize this energy to do work in different forms. We
know all matter is made up of atoms and molecules, these atoms or molecules
always in motion like vibrating itself in the matter or colliding with each
other, etc. this motion results in heat energy formation. And we can physically
quantify the amount of heat in terms of temperature.
The heat will flow from a higher temperature region to lower temperature region when they are not in
thermal equilibrium. The mode of this heat flow or heat transfer can happen
in three ways, conduction, convection, and the radiation. Let’s see each mode of
heat transfer,
Conduction.
It can be defined as
the mode of heat transfer occurs when the two objects having different
temperature are in contact with each other. The heat will flow from higher
temperature to lower temperature until the temperature of the object became the same. By using Fourier’s law of heat conduction we can find the heat flow rate
by conduction, i.e.
Q
= -k x A (dT/dx)
Where Q is the heat
flow rate.
K is the thermal conductivity of the material.
A is the cross-sectional area normal to the heat flow
direction.
dT/dx is the temperature gradient of the section.
Convection.
It can be defined as
the mode of heat transfer occurs in the liquid or gaseous stage. Convection occurs when
the warmer area of liquid or gas move rises up and the heat gets transferred until
the temperature equals the source temperature. By using Newton’s law of cooling
the convective heat transfer can be found out, i.e.
Q
= h x A (Ts-Tα).
Where Q is the
convective heat flow rate.
'h' is the coefficient of convection.
A is the cross-sectional area.
Ts is the surface temperature.
Tα is the outside temperature.
Radiation.
Here the heat gets
transferred in the form of radiant energy or by means of wave motion, it
doesn’t require any medium for heat transfer. By using Stefan-Boltzmann law, we
can find the rate of heat radiation that can be emitted by a surface at
thermodynamic temperature. i.e.
Q
= σ x T 4
Where Q is the rate of
heat radiation.
σ
is the Stefan-Boltzmann constant.
T is the absolute temperature of the surface.
Understanding the basics makes to solve the complex problem.....
The Versatile Chapter
