TRANSFER OF THERMAL ENERGY
THERMAL ENERGY
➢ This is the energy possessed by a body due to its temperature.
When there is a temperature difference between two object, thermal energy in the form of heat flows
through them. In this chapter we shall investigate the mechanisms by which thermal energy is transferred from one place to another.
WAYS OF HEAT TRANSFER
1. Conduction
2. Convection
3. Radiation
1. CONDUCTION OF HEAT
➢ This is the transfer of heat through matter (solids) from a region of high temperature to a region of
low temperature without actual movement of the medium.
❖ Conduction is characterized by the movement of energy from atom to atom without the bulk
movement of matter.
❖ Conduction is the primary mode of heat transfer in solids but can occur to a lesser extent in liquids.
GOOD AND BAD CONDUCTION OF HEAT
a) GOOD CONDUCTION OF HEAT
➢ Are those materials that allow heat to flow through them easily.
Examples of good conductors are metals such as Cu, Ag, Fe, Al, Pb, and brass.
b) BAD CONDUCTION OF HEAT (THERMAL INSULATORS)
➢ Are those materials that do not allow heat to flow through them easily.
Examples of bad conductors are non-metals such as wood, glass and plastics.
FACRORS AFFECTING THE RATE OF CONDUCTION OF HEAT
i) Length of the material
ii) Difference in temperature between the two ends of the material
iii) The cross-sectional area
iv) Thermal conductivity of the material
I) LENGTH OF THE MATERIAL
The rate of conduction of heat is inversely proportional to the length of the material.
Thus; the longer the material the more the time it will take to conduct heat through it.
II) DIFFERENCE IN TEMPERATURE BETWEEN THE TWO ENDS OF THE MATERIAL
The rate of conduction of heat is directly proportional to the temperature between the ends of the material.
III) THE CROSS-SECTIONAL AREA
The longer the cross-sectional area the faster the rate of heat conduction
IV) THERMAL CONDUCTIVITY OF THE MATERIAL
The higher the thermal conductivity of the material the higher the rate of heat conduction
MINIMIZING HEAT LOSS BY CONDUCTION
Heat loss by conduction can be minimized by
a) Using thermal insulation.
❖ Thermal insulation is used in boilers, hot-water pipes and in the textile industry.
b) In house, insulating against heat loss is achieved using double-glazed windows, carpets, curtains
and draught excluders.
