Difference Between Conduction and Convection

Conduction vs Convection | What is Conduction? What is Convection?

Conduction and convection are two phenomena encountered in heat and thermodynamics. These two concepts are very important when it comes to understanding of heat transfer. Radiation along with conduction and convection make up the three forms of heat transfer. Fields like thermodynamics, heat engines, artificial weather systems, meteorology, and even our physiology depend on the principles of conduction and convection. It is vital to have a good understanding in conduction and convection along with radiation in order to have a good understanding of these fields. In this article, we are going to discuss what conduction and convection are, the reason for conduction and convection, their similarities, what are the daily incidents we can observe due to conduction and convection, their similarities and finally their differences.

What is Conduction?

Conduction is defined as the transfer of thermal energy between regions of matter due to a temperature gradient. Conduction can happen in any material, but as far as the practice is concerned, conduction is only applied to solids. When solids are heated, atoms and molecules inside the solid vibrate due to the kinetic energy received from heating, the collisions of these vibrating atoms with the neighboring atoms causes the neighboring atoms to vibrate, hence, the vibrations are transferred into the other end of the solid. The atoms at the surface of the solid release the energy from the vibration to the open space. For a uniform rod in a steady state with sides insulated and only the two ends are exposed, the rate of heat flow is directly proportional to the area of the heat absorption and temperature gradient. The steady state is when there is thermal equilibrium between all of the points, which means, the temperature of a point does not vary with time. Gasses and liquids also show conduction, but this is in the form of direct molecule collisions. They do not vibrate like solids.

What is Convection?

Convection is the terminology used for bulk movements of fluids. However, in this article convection is taken to be in the form of heat convection. Unlike conduction, convection cannot take place in solids. Convection is the process of transferring energy through direct matter transfer. In liquids and gasses, when heated from the bottom, the bottom layer of the fluid will be heated. The heated air layer then expands, being less dense than the cool air; the hot air layer rise in the form of convection current. Then the next fluid layer is experiencing the same phenomena. Meanwhile, the first hot air layer is now cooled down, and it will come down. This effect creates a conduction loop, continuously releasing the heat taken from the lower layers to the upper layers. This is a very important pattern in weather systems. The heat from the surface of the earth is released to the upper atmosphere in this mechanism.

What is the difference between Conduction and Convection?

• Conduction happens in all media, while convection is not possible in solids.

• Convection involves flow of matter in bulks while conduction involves matter vibrating about a fixed point.

• In a closed system, heat loss by convection is not possible but heat loss from conduction is possible.

  • R Christopher Aversa

    “In a closed system, heat loss by convection is not possible but heat loss from conduction is possible.”

    How is it possible to lose heat (by any method) in a closed system? Doesn’t the very nature of the system being closed prohibit heat from being transferred in or out?