Modes of Heat Transfer

Heat is a type of energy that starts at the molecular level and works its way up. When power is added to a substance, the molecules of that substance move in one direction or another. While molecules start vibrating upon being heated, they pass on the heat to their surrounding molecules, making them vibrate as well. 

Heat energy can move from one body to another or from one location of a body to another, as long as there is enough heat. Studying how heat energy is passed on is called heat transfer. There must be a temperature differential between two bodies for heat to travel between them. The two bodies must be at two different temperatures, one higher than the other, so that that heat can move from the one with higher temperature to the one with lower temperature.

Different Modes of Heat Transfer

When we boil water in a pan over an open flame, the temperature increases; it begins to cool when the stove is switched off. The water is in the pan, and the flame is transferring heat. Heat always passes from the heated matter to the colder ones. 

Transfer of heat happens when objects fall at different temperatures or if there is an object separate from the rest of the world. This occurs when the object and the rest of the world reach a temperature equally.

There are three ways of transferring heat. Examples of how heat moves through them are also described below:

1. Conduction
2. Convection
3. Radiation

Conduction

A gas burner is used to heat one end of the metal bar. After a time, the other end of the bar becomes heated because heat travels from the hot end to the cold end of the bar. The molecules (or particles) of the metal bar don’t move. This is how conduction transfers heat within an object.

Definition of conduction

When heat moves from a hot part to a colder part of the material without the particles moving in conduction, it is heat transfer through conduction. Heat moves through solids, especially metals, only by conduction. Temperature conduction is a big part of how we live our daily lives. Some examples of how thermal conduction can be used in real-world situations are: 

(a) Wooden handles are used on cooking utensils to prevent the hands from touching the hot metal.

(b) It takes a lot of blocks of ice to make a two-storey igloo for the Eskimos.

Convection

Convection is the movement of the heated molecules by the body. People use convection to move heated particles from one place to another, which carries the heat from one place to another. However, it is most noticeable when it comes to liquids and gases. Land and sea breezes are made by convection, and they happen all over the place. It also plays a significant role in the ventilation, electricity, heating of buildings, etc.

So, when you heat water in a pot, the heated molecules become lighter and move up, which means the water will rise. Warmer and denser water molecules start to move up, and colder and denser water molecules start moving down.

Types of Convection

• Forced convection

 If a fan, pump, or the wind is used to compel the fluid to flow across the surface, it is termed forced convection.

• Convection, natural or free

Natural (or free) convection, on the other hand, occurs when fluid motion is produced by buoyancy forces generated by density changes caused by temperature variations in the fluid.

Radiation

Radiation is the transfer of heat from one location to another without using a medium such as water or electricity. Between us and the sun’s rays, there is no intermediary. Heat radiation can pass through a vacuum too. They have the same properties as light. Heat radiations are also a part of the range of electromagnetic waves. It does not take anything to move heat by radiation. Radiation is how the energy from the sun gets to us.

Conclusion

Heat transfer refers to the phenomenon of transferring energy from one point to another. This specific mechanism includes heat conduction, convection, and radiation heat transfer. Conduction is the process of transfer of heat during the heat conduction process, which is a slow process.  For instance, if one end of a metal rod is held above a flame, the other end, which has not been in contact with the flame, will soon turn hot as well. This is due to conduction, enabling the heat to travel through the entirety of the rod. The molecules at regions which are hotter have more kinetic energy than those which are not hot. Radiation heat transfer refers to the transmission of electromagnetic radiation. The energy radiated by electromagnetic radiation is called radiant energy. The molecules in a liquid vibrate faster when heated, and at a higher temperature, these molecules begin to expand to occupy their space. When the liquid is heated, less dense fluid begins to rise to the surface, the cooler fluid takes its place. And this repeated rising and falling between warmer liquids and cooler liquids sets up the convection current.