Heat exchangers are devices designed to transfer heat from one fluid to
another without the fluids coming into contact. There are a wide variety of
applications for heat exchangers, for example: radiators, air conditioning and
power plants.
Mechanism of Heat Transfer by Conduction
The transfer of heat energy
by conduction takes place within the boundaries of a system.
The rate equation which
describes this mechanism is given by Fourier Law
Where = rate of heat flow in X-direction by conduction
in J/S or W,
k = thermal conductivity of
the material. It quantitatively measures the heat conducting ability and is a
physical property of t he material that depends upon the composition of the
material, W/mK,
A = cross-sectional area
normal to the direction of heat flow, m2,
dT/dx = temperature
gradient at the section,
Thermal Conductivity of Materials
Thermal conductivity is a
physical property of a substance and In general, It depends upon the
temperature, pressure and nature of the substance. Thermal conductivity of
materials are usually determined experimentally and a number of methods for
this purpose are well known.