Best practice guidelines for heat transfer simulations

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Heat Transfer is a engineering branch which deals with flow of Heat through any material.
Heat is form of energy that gets transformed from a body at higher temperature to a body a lower temperature.
There are three modes of heat transfer namely- Conduction, Convection and Radiation.

Conduction takes place due to two mechanisms in the solids. They are inter molecualar interaction and by drift of free electrons. When there is a temperature difference the molecules starts moving from place to place and results in the interactions where the energy exchange takes place between these molecules which results in energy transfer. The other way is, if you fundamental knowledge of the nucleas, every substance having nucleas and number of orbits surrounding it like planets surrounding sun. As we go far from the nucleas the molucules having less energy. So when there is a temperature difference, the electrons will shift from one energy level to other energy level which results in the energy difference. These are the two ways by which the conduction heat transfer takes place. Fourier law governs the conduction heat transfer.

Convection heat transfer exists only when there is a motion of fluid from place to place on a solid. When a fluid is moving on a solid (say both are at the different temperature), there exists a temperature gradient between these two media and results in the energy transfer. If this fluid motion is created by some external agents like fan or pump, it is forced convection and if the fluid motion arises because of the density variation and there by due to buyoyancy effects, it is free convection. Newtons law of cooling governs the convection heat transfer. 

Radiation heat trasfer doesn't require any type of media. In this mode the energy transfer takes place through the electro magnetic waves. Radiation heat transfer will exists only at higher temperatures and it will be maximum in the vaccum. Stefan's Boltzman law governs the Raditation heat transfer.