View Factor in radiation heat transfer

In summary, view factor, also known as shape factor, is a dimensionless quantity that represents the fraction of radiation emitted from one surface that reaches another surface. It is calculated using the equation F<sub>AB</sub> = A<sub>1</sub>A<sub>2</sub>cosθ/πr<sub>AB</sub><sup>2</sup>. View factor is important in radiation heat transfer as it helps us understand how the geometry and arrangement of surfaces affect the heat transfer process. The shape and orientation of surfaces greatly influence the view factor, which can range from 0 to 1 and cannot be greater than 1.
  • #1
dkdhiraj
1
0
Hi
can anyone temme how to calculate view factor between two spheres.
 
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  • #2
Are the spheres concentric and at uniform temperature? How have you tried to start this problem?
 
Last edited:
  • #3
This migh be of any help

see attachment.

Solution by
Thermal Radiation Heat Transfer
Robert Siegel and John Howell

Reference: Juul (1976); Felske (1978); Chung and Naraghi; Grier; Campbell and McConnell; Farnbach; Jones
 

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  • #4
hi..can anybody send me the article of Howell R. "monte carlo strategies for radiative transfer in participating media" this is in a book but in our library, this book is not available...
 

What is view factor in radiation heat transfer?

View factor, also known as shape factor, is a dimensionless quantity that represents the fraction of radiation emitted from one surface that reaches another surface. It takes into account the geometric arrangement and orientation of the two surfaces, as well as their relative sizes and distances.

How is view factor calculated?

The view factor between two surfaces A and B can be calculated using the following equation:
FAB = A1A2cosθ/πrAB2
where A1 and A2 are the areas of surfaces A and B, θ is the angle between the normal vectors of the two surfaces, and rAB is the distance between them. This equation is based on the assumption that the surfaces are diffuse emitters and receivers of radiation.

Why is view factor important in radiation heat transfer?

View factor is a crucial factor in determining the amount of heat transfer between two surfaces by radiation. It helps us understand how the geometry and arrangement of surfaces affect the heat transfer process. By knowing the view factors, we can calculate the net heat transfer between surfaces and design more efficient heat transfer systems.

How does the shape and orientation of surfaces affect view factor?

The shape and orientation of surfaces greatly influence the view factor between them. Surfaces that are facing each other directly have a higher view factor compared to those that are at an angle. Similarly, surfaces with larger areas and closer distances have higher view factors. Irregular or complex-shaped surfaces may have more complicated view factor calculations.

Can view factor be greater than 1?

No, view factor is a dimensionless quantity and its value ranges from 0 to 1. A value of 1 indicates that all the radiation emitted from one surface reaches the other surface without any obstruction. A value of 0 means that there is no direct line of sight between the two surfaces, hence no radiation transfer.

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