Heat Transfer Convection

You’ve probably noticed that a hot glass of water will become cold after a period of time. It occurs as a result of the heat being lost to the environment. In this way, we can define heat transfer as the transfer of thermal energy between two physical systems (or systems of physical systems). In the event of a temperature difference, heat is transferred from a hot system to a colder system.

The actual physical movement of a substance containing thermal energy from one location to another, resulting in the transfer of thermal energy between the two locations. When it comes to liquids and gases, heat convection is frequently the primary mode of energy transfer. The boiling of water in a pot is a well-known example of convectional heat transfer. Convection is a term that refers to the non-radiative heat exchange that occurs between a surface and a fluid that is flowing over it. Although heat transfer by conduction occurs in this process as well, the energy transfer by flow of the fluid hence the name convection is the dominant feature that regulates the process. One of the three fundamental methods of heat transfer, the other two being conduction and radiation, convection is one of the most common.

An introduction to the concept of convection

As defined by the Principle of Heat Transfer, Convection is “the procedure of heat transfer associated with the motion of molecules in fluids such as liquids and gases.” Convection is also known as “molecular motion” in some cases. Conduction is the primary mode of heat transfer between a fluid and an object at the outset. Bulk heat transfer, on the other hand, occurs as a result of fluid movement.”

Factors to consider to keep in mind

In normal circumstances, liquids and gases are poor heat conductors because of their density. 

The heat transfer in this method occurs through advection, diffusion, or a combination of the two.

Because there is no movement of particles in solids, convection does not take place. Thermal conduction, also known as diffusion, is the process by which heat is transferred in solids.

What is the mechanism by which heat is transferred through the process of convection?

The thermal expansion of the fluid occurs as a result of the heating of the fluid at the lower level. As a result of the process of buoyancy, the fluid below becomes less dense and the hotter portion rises to the surface. Denser and colder fluids are replaced by the hot fluid. When that portion of the mixture becomes heated and rises, the process is repeated. As a result, it changes once more due to the colder upper layer. Heat is transferred through convection in this manner.

Types of Convection

During the energy release process, there are primarily two types of heat transfer convection that are observed.

These are the ones:

Natural convection is defined as the convection that occurs as a result of the buoyant force associated with the difference in densities caused by the difference in temperature. Natural convection can be seen in the form of the oceanic wind.

Forced convection is created by external systems such as pumps and fans, and is referred to as forced convection  Forced convection can be found in the use of a geyser or water heater to heat water, as well as the use of a fan during the summer months.

Ideal Examples of Heat Transfer Convection

The simplest and most common examples of natural convection are wind and breeze off the land or from the sea.

Sea Breezes and Land Breezes

Sea breezes are most common during the daytime. Both land and sea are heated by the sun. Furthermore, the sea, which has a greater heating capacity than the land surface, absorbs more solar energy but warms up more slowly than the land surface. As a result, the temperature above the land rises, heating the air above it. Furthermore, warm air expands because it is less dense than cold air, resulting in low pressure over the land near the coast. The difference in air pressure causes the air to flow from the sea to the land. Finally, the sudden gust of wind is referred to as a sea breeze.  The process takes place at night due to the land breeze. Both the sea and the land become cooler. As a result of the difference in heat capacity between land and water, land loses heat more quickly than water. Because the temperature of the sea is higher, the air pressure is also lower. The term “land breeze” refers to a cool breeze that comes from the land.

Conclusion

Because of the movement of fluid, convection is the process by which heat is transferred from one location to another. Despite the fact that it is frequently discussed as a separate method of heat transfer, convective heat transfer is actually the result of the combined processes of conduction and convection. When it comes to heat transfer in liquids and gases, convection is typically the dominant mode of heat transfer.