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Equivalent
Resisitance Method - Heat Transfer
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[ Heat
Transfer Table of Contents]
It is possible to compare heat transfer to
current flow in electrical circuits. The heat transfer rate
may be considered as a current
flow and the combination of thermal conductivity, thickness
of material, and area as
a resistance to this flow. The temperature difference is the
potential or driving
function for the heat flow, resulting in the Fourier equation
being written in a form similar
to Ohm’s Law of Electrical Circuit Theory. If the thermal
resistance term Dx/k is written
as a resistance term where the
resistance is the reciprocal of the thermal conductivity
divided by the thickness
of the material, the result is the conduction equation being
analogous to electrical systems
or networks. The electrical analogy may be used to solve
complex problems involving both
series and parallel thermal resistances. The
illustration given below, shows the equivalent
resistance circuit. A typical conduction problem in its
analogous electrical form is given
in the following example, where the "electrical"
Fourier equation may be written as follows.
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