Convection vs Radiation
Convection and radiation are two processes discussed on the field of heat. Convection is the method of transferring heat using moving particles. Radiation does not require particles or a medium to transfer energy. Both of these processes are very important in numerous fields. These concepts are widely used in heat and thermodynamics, atmospheric science, weather analysis, climate analysis, fluid mechanics and even medical sciences. It is vital to have a proper understanding in these concepts in order to excel in such fields, which have heavy usage of these concepts. In this article, we are going to discuss what convection and radiation are, their definitions, applications of convection and radiation, their similarities and finally the difference between convection and radiation.
What is Radiation?
Electromagnetic radiation or commonly known as radiation or EM radiation is a method of heat transfer. Electromagnetic radiation was first proposed by James Clerk Maxwell. This was later confirmed by Heinrich Hertz who successfully produced the first EM wave. Maxwell derived the wave form for electric and magnetic waves and successfully predicted the speed of these waves. Since this wave velocity was equal to the experimental value of the speed of light, Maxwell also proposed that light was, in fact, a form of EM waves. Electromagnetic waves have both an electric field and a magnetic field oscillating perpendicular to each other and perpendicular to the direction of wave propagation. All electromagnetic waves have the same velocity in vacuum. The frequency of the electromagnetic wave decides the energy stored in it. Later it was shown using quantum mechanics that these waves are, in fact, packets of waves. The energy of this packet depends on the frequency of the wave. This opened the field of wave – particle duality of matter. Now it can be seen that electromagnetic radiation can be considered as waves and particles. An object, which is placed in any temperature above the absolute zero, will emit EM waves of every wavelength. The energy, which the maximum number of photons emitted, depends on the temperature of the body.
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 first. 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 Convection and Radiation?
• For convection to occur, a medium with movable particles must be present around the heated body. Radiation does not require any medium.
• The heat transfer from radiation is faster than the heat transfer from convection.
• Convection always carries the heat away from the gravity, whereas radiation is emitted in every direction.