Heat Transfer Methods

Heat Transfer

This is a thermodynamic fact of life -- if there are two objects with different temperatures together, then heat transfer will cause them to reach the same temperature.


Conduction

In heat transfer, conduction (or heat conduction) is the transfer of thermal energy between neighboring molecules in a substance due to a temperature gradient. It always takes place from a region of higher temperature to a region of lower temperature, and acts to equalize the temperature differences.

Conduction takes place in all forms of matter, viz. solids, liquids, gases and plasmas, but does not require any bulk motion of matter. In solids, it is due to the combination of vibrations of the molecules in a lattice and the energy transport by free electrons. In gases and liquids, conduction is due to the collisions and diffusion of the molecules during their random motion.

 

Radiation

Thermal radiation is electromagnetic radiation emitted from a material which is due to the heat of the material, the characteristics of which depend on its temperature. Thermal radiation is generated when heat from the movement of charges in the material (electrons and protons in common forms of matter) is converted to electromagnetic radiation.

 

Convection

Convection is the movement of molecules within fluids (i.e. liquids, gases). It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids.

Convection is one of the major modes of heat transfer and mass transfer. Convective heat and mass transfer take place through both diffusion – the random Brownian motion of individual particles in the fluid and by advection.