Hello dear Pisipaty Srinivas Kishore

I know many people can give good answers to this question, along with some links to relevant resources. However, instead of giving details, I will prefer to answer it slightly differently (since I am relaxed that some others can give the required good answers).

1. Some theory and techniques required and matured in some other field may later be found useful in some other fields. There are many examples for this.

2. In electrical engineering, if in a circuit much power is consumed on a device (e.g. transistor, chip, etc.), the excess heat may damage the device, so a "heat sink" is usually needed (heat sink: a metal piece with large surface area fitted onto the device's case to help the device release the heat easier).

When choosing the heat sink, the analysis is based on the heat transfer from the physical device (e.g. transistor's junction) to the device case, then to the heat sink and finally to the air. An electrical engineer makes this analysis by building an analogy between the heat transfer and resistive electrical circuits. This is where "heat transfer" and "electrical circuit" concepts meet closer, because the engineer uses the electrical circuit analysis methods for both electrical circuit analysis and for heat transfer analysis.

Best regards...

In heat transfer several layers of materials can be seen as analog to resistances in serie in electricity, so a thermal resistivity or conductance can be defined and the same rules apply as for an electrical circuit: the total resistance will for instance be the sum of the resistance in series (same for parallel). The equivalent of the electrical intensity is then the heat flux and the electrical potential is replaced by the temperature and it works for quite simple configurations. Rules to add intensities and resistivity are usually most well known for electricity than for heat fluxes and thermal resistivity.

One-dimensional heat flow equations (in steady-state, of course) look very similar to the Ohm's law equations: temperature differences are similar to voltage differences, heat flux (Watts per square meter) is similar to electric current, and thermal resistances [Kelvin/(Watts per square meter)] are similar to electric resistances. One-dimensional steady-state heat flux equals temperature difference divided by thermal resistance (which equals thickness divided by thermal conductivity). And steady-state heat flux through a multi-layer wall equals the total temperature difference divided by the total sum of thermal resistances of all the layers (each equals thickness of the layer divided by its material's thermal conductivity) and sum of thermal contact resistances between all the layers.