Surface area dependence of radiative heat transfer

In summary, the dependence of radiative transfer from a body is primarily based on its surface area rather than its volume due to Stefan's law, which is an approximation for an ideal black body. This is because the charges responsible for emitting electromagnetic radiation are concentrated in the surface layer of the body, and the body's volume does not affect the emission significantly. However, for non-ideal black bodies, there may be some emission from deeper layers, but it is effectively canceled out.
  • #1
Karthiksrao
68
0
Hi all

I was just wondering about the dependence of radiative transfer from a body, on its surface area and not the volume. As per stefan's law, the variation is (StefanConstant * SurfaceArea* Temp^4)

The primary source of these electromagnetic radiation is from the charges in the body that are vibrating at a particular temperature. And the amount of charge would obviously depend on the volume of the body. Higher the volume, you would expect more charges to be vibrating, and hence higher would be the emitted radiation.

If that be the case, why is the net radiative transfer dependent on the surface area of the body and not the volume ?

Any thoughts ?
Thanks a lot!
 
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  • #2
Stefan's law is an approximation of 'ideal black body' - the body having so large amount of various vibrating charges, that very thin (infinitesimaly thin) layer of that body emits all that radiation, but, at the same time, it absorbs radiation emitted from deeper layers.

If you take not so perfectly black body - then you'll have some emission coming from deeper parts of the body, as the surface layer is not able to absorb all the light from deeper layers. But, on the other hand, every layer also emits less. Effectively, those effect cancel, so black body idealisation may be used as an approximation.
 

Related to Surface area dependence of radiative heat transfer

1. What is radiative heat transfer?

Radiative heat transfer is the process by which heat is transferred between two objects through electromagnetic radiation. This is different from conductive and convective heat transfer, which involve direct contact or movement of a medium, respectively.

2. How does surface area affect radiative heat transfer?

The surface area of an object has a direct impact on the amount of radiative heat transfer that occurs. This is because a larger surface area allows for more radiation to be emitted or absorbed, leading to a higher rate of heat transfer.

3. What is the relationship between surface area and radiative heat transfer?

The relationship between surface area and radiative heat transfer is directly proportional. This means that as the surface area increases, the amount of heat transfer also increases. Similarly, if the surface area decreases, the heat transfer will decrease as well.

4. How does surface material affect radiative heat transfer?

The material of an object's surface can also impact radiative heat transfer. Some materials are better at absorbing and emitting radiation than others, which can affect the rate of heat transfer. For example, dark and rough surfaces tend to have a higher radiative heat transfer than light and smooth surfaces.

5. How can understanding the surface area dependence of radiative heat transfer be useful?

Understanding the surface area dependence of radiative heat transfer is important in many fields, including engineering, materials science, and climate science. It can help in designing more efficient heat exchange systems, predicting the temperature of objects in different environments, and understanding the Earth's energy balance.

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