Thermal Radiation Energy transfer

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SUMMARY

The discussion centers on the concept of net thermal radiation, defined by the equation Pnet = Pabs - Prad = σϵA(Tenv^4 - T^4). Participants clarified that when the environmental temperature (Tenv) exceeds the object's temperature (T), Pnet can be negative, indicating that incoming radiation energy surpasses outgoing radiation energy. A critical point raised was an error in the reference materials, where the temperatures were incorrectly presented, leading to confusion regarding the net radiation calculation.

PREREQUISITES
  • Understanding of thermal radiation principles
  • Familiarity with the Stefan-Boltzmann law
  • Knowledge of emissivity and its impact on radiation
  • Basic grasp of thermodynamic temperature scales
NEXT STEPS
  • Study the Stefan-Boltzmann law in detail
  • Explore emissivity values for different materials
  • Learn about the implications of negative net thermal radiation
  • Review common errors in thermal radiation equations
USEFUL FOR

Physicists, engineers, and students studying thermodynamics or heat transfer, particularly those focusing on thermal radiation concepts and calculations.

Awer1
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I have a general question regarding Radiation. If the net Thermal Radiation is understood to be :

Pnet = Pabs - Prad= σϵA(Tenv^4 - T^4) . How is it that Pnet is negative if the environmental temp is higher than the temp of the object?
 
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Awer1 said:
I have a general question regarding Radiation. If the net Thermal Radiation is understood to be :

Pnet = Pabs - Prad= σϵA(Tenv^4 - T^4) . How is it that Pnet is negative if the environmental temp is higher than the temp of the object?

Because the incoming radiation has more energy than the outgoing radiation. I can't see what the problem is.
 
I figured it out with some help, the equation in the book and their website had the equation wrong.. the book had the temperatures flipped
 

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