Hi all :
Please, I need some help on Heat Radiation Transfer:
How I can derive the formula of the View Factor for a particular configuration, in a way of ending with an expression for the VF as a function of the geometrical parameters (dimensions, shapes and orientation) of the bodies involved ? Starting from general expression for the View Factor (Eq. attached)
Does anyone have derived such kind of expression for a given 'complex' configuration, starting from the general equation ?
Thank you for the Help
Best Regards !
Hello Franklin Uriel Parás Hernández ,
Normally, people try not to solve the inetgrals for the view factors unless there is no other alternative. Usually, one can evaluate the view factors, without performing integrations, by the following ploy. First, write the matrix of view factors for all the surfaces in your system, e.g., Fii would be the view factor for surface i, while Fij will be the view factor for surface i seeing (transferring energy) to surface j. Many times the Fii can be solved by inspection, e.g., a spherical surface inside a larger spherical surface has a view factor of zero because the smaller spherical surface cannot 'see' itself, i.e., F11 = 0, where index 1 refers to the smaller spherical surface. The off diagonal view factors, Fij, are related by the general view factor integrals to the following reciprocity relation: AiFij = AiFji, where Ai is the area of surface i. There is also a conservation equation for the enclosure and the internal surfaces. Using all these relationships can allow one to avoid caculating all but a few - sometimes none - of the integrals, see the following book:
Frank P. Incropera, David P. DeWitt; Fundamentals of Heat and Mass Transfer, Second Edition; John Wiley & Sons, Inc.; 1985; pp. 624-635.
Regards,
Tom Cuff
Hello Franklin Uriel Parás Hernández,
I suggest you to see this clip: https://www.youtube.com/watch?v=bOFyMAZMHkE
Regards,
Luca Mauri
You need to familiarize yourself with the basics, as explained in textbooks on radiative heat transfer, e.g. Hottel & Sarofim's Radiative transfer, or Siegel&Howell's Thermal radiation heat transfer.
See also http://www.thermalradiation.net/indexCat.html,
https://www.researchgate.net/publication/320805157,
Article A novel teaching program for inter-surface radiation exchange
Article Finite-element view-factor computations for radiant energy exchanges
- Badges
- Science topic
- Similar topics
- Engineering
- Thermal Engineering
- Thermofluid
- Heat Transfer