Thermal Radiation from a Liquid or Gas

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SUMMARY

This discussion focuses on calculating heat loss from gases or liquids, emphasizing that it is a gray-body problem rather than a simple blackbody problem. The total power radiated can be determined by multiplying the temperature-weighted blackbody curve with the spectrally-weighted emissivity, integrated across all wavelengths. Additionally, the conversation highlights that conduction and convection also contribute to heat transfer, complicating the calculations based on geometry. References to Rohsenow & Hartnett provide foundational insights into these heat transfer processes.

PREREQUISITES
  • Understanding of gray-body and blackbody radiation concepts
  • Familiarity with emissivity and its spectral dependence
  • Knowledge of heat transfer mechanisms: conduction and convection
  • Basic proficiency in integrating functions over wavelengths
NEXT STEPS
  • Research the principles of gray-body radiation and its applications
  • Study the integration of temperature-weighted blackbody curves
  • Explore the heat transfer equations from Rohsenow & Hartnett
  • Investigate numerical methods for solving complex heat transfer problems
USEFUL FOR

Engineers, physicists, and researchers involved in thermal analysis, heat transfer calculations, and those seeking to optimize thermal management in fluids.

radiatorguy
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Hello,

I've been trying to find out how to calculate heat loss from a gas or liquid vs. temp. My understanding is that this is not a simple blackbody problem for a variety of reasons... guess it's more a gray-body problem. Have not been successful at finding papers or texts which deal with this specific issue. Are there simple ways to get approximate solutions to this problem or is this much simpler than I realize. Any insights or leads would be appreciated.

Thanks
 
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Radiation heat losses are reasonably straightforward to calculate- the total power radiated is a product of the temperature-weighted blackbody curve with the spectrally-weighted emissivity, integrated over all wavelengths.

There can be other processes- conduction and convection- that cause heat transfer as well. Those can be much more complicated, depending on the geometry.
 
Rohsenow & Hartnett
 
Thanks for the help Andy and Bystander.
 

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