Conduction Heat Transfer

Conduction heat transfer is the heat transfer through medium without accompanied by displacement of the particle medium. Conduction usually can occur in solids such as various types of metal and glass. For example, if one end of metal is heated, the other end of metal will also feel hot because heat transfer process from one end to other end.

The existence of temperature gradient will make heat transfer process occur. Heat transfer in solids arises due to movement between atoms at high temperature, so that the atoms can move heat. In liquids or gases, the hot is distributed by the collisions between molecules.

Basic equation of conduction heat transfer:

q = rate of heat transfer
k = thermal conductivity
A = sectional area of ​​dT

The basic relation through conduction heat flow is comparison between rate of heat flow across isothermal surface and gradient contained on the surface which valid at every point in an object at any point in an object on any time which is known as Fourier law as follow:

A = isothermal surface area
n = distance, measured normal (perpendicular) to the surface
q = rate of heat flow across the surface in normal direction
T = temperature
K = thermal conductivity

Proportionality constant (k) is the physical properties of material that is called thermal conductivity. The unit used in thermal conductivity is Cal/cm Sk. To convert this unit to Btu/ft hour ºR is multiplied by 242.9 and to transform into W/cm K or J/cm Sk is multiplied by 4.1866. Based on the formula, it can be carried out measurements in an experiment to determine the thermal conductivity of various materials. Generally, thermal conductivity is highly dependent on temperature.

No comments: