Heat Transfer Terminology

In the simplest terms, the stream of heat transfer is regarded with only two things: temperature, and the flow of heat. The temperature symbolizes the quantity of thermal energy available, while heat flow symbolizes the movement of thermal energy from place to place.

On a microscopic scale, the thermal energy is associated to the kinetic energy of molecules. The higher is the material's temperature, the higher the thermal agitation of its constituent molecules (i.e., manifested both in linear motion and vibrational modes). It is natural for areas having greater molecular kinetic energy to pass this energy to areas with less kinetic energy.

Numerous material properties serve to adapt the heat transferred among two areas at differing temperatures. Illustrations include thermal specific heats, conductivities, material densities, fluid viscosities, fluid velocities, surface emissivities, and many more. Taken altogether, such properties serve to make the solution of various heat transfer troubles an included process.

To recognize and correspond in the thermal science field, certain terms and expressions should be learned in heat transfer as illustrated below.

Blackbody:

The blackbody is a surface which absorbs all incoming radiation; which is, it does not reflect radiation. The blackbody also releases the maximum possible radiation.

Conduction:

The heat conduction occurs via various mechanisms in various media. Hypothetically, conduction occurs via collisions of molecules in a gas, via oscillations of each molecule in a "cage" produced by its nearest neighbors in a fluid, and through the electrons carrying heat in metals or by molecular motion in other solids. Usual for heat conduction is that the heat flux is relative to the temperature gradient.

Convection:

The word convection is employed for the heat indulgence from a solid surface to a fluid, where the heat transfer coefficient and the temperature difference transversely a fictitious film explain the flux.

Specific heat:

The material property which indicates the quantity of energy a body stores for each degree rise in temperature, on per unit mass basis. The unit is J/kg-K.

Thermal conductivity:

The material property which explains the rate at which the heat flows inside a body for a particular temperature difference. Its unit is W/m-k.