Thermal energy is being transferred in three different methods. They are convection, conduction and radiation. If two materials of different temperature are placed together, they will try to achieve a thermal balance. This is the reason that temperature moves from higher level to lower level. This means that an object will become cooler after dissipating the heat. In this process, the object transfers its heat to a colder object to reach an equilibrium level of temperature. The moment two materials achieve the same level of temperature they will remain in that position till any outer change or force is being applied.
The process of generating thermal energy in a material through the process of molecule collision is called the conduction. The molecules of an object that has a higher thermal energy tremble quicker than the object that has lower thermal energy. This movement causes a collision of the molecules and assists the transfer of the energy. Common incidents of conduction can be seen in daily life, for example, if a metal spoon is placed in a hot liquid the molecules of the hot liquid tremble against the molecules of the spoon and make the spoon hot.
Radiation is another way of transferring thermal energy. The thermal energy is transferred to the objects through infrared rays. This is the same way in which the heat of the sun makes the surface of the Earth hot. In this process, the heat can be felt as the infrared rays hit the molecules of the air and make them hot.
Convection is the third way of transferring the thermal energy. In this process, the high temperature is absorbed by the liquids or the fluids. Both natural form and forced convection is used for transferring thermal energy.
When any liquid is placed on a hot surface, the liquid will become hot after a certain time. If we look at this process carefully, then we can see that the hot surface causes the molecules of the liquid to tremble. When this happens, the molecules become bigger and allow the heated molecules to move up. The cooler liquid moves downwards and this rotation continues until the whole liquid reached in a balanced temperature position. This process of rotation is known as the convection current and is also responsible for weather changes and climatic changes.
The forced convection happens, when some mechanical power such as pump or fan forces a liquid to move and transfer temperature from one object to another.
The principals of thermodynamics assist us to utilize thermal energy from various sources for our own uses. We are now trying to make various devices that enable us to transfer the energy or even store the thermal energy naturally. Thermal energy is a viable and alternative source of energy as compared to fossil fuels. This is the reason, that solar energy or wind energy is being touted as clean forms of energy as compared to fossil fuels that emanate pollution and waste. Wind energy and solar energy are now been tapped for use in many industrial applications also.