Define view factor in heat transfer?

The view factor, also known as the configuration factor or shape factor, is a dimensionless quantity used in heat transfer to describe the proportion of radiation leaving one surface that directly reaches another surface. It is essential in calculating radiation exchange between surfaces in a geometrical arrangement. The view factor depends on the geometry and orientation of the surfaces involved and is typically used in the context of radiative heat transfer calculations. In a closed system, the sum of view factors from one surface to all other surfaces equals one.