VDI Heat Atlas · K2 View Factors


The view factor ϕ 12 is a purely geometrical value which describes the fraction of the total radiation from a surface 1 that hits another surface 2; see Sect. 2.2 in Chap. K1 . So in almost all cases of thermal radiation heat transfer, the first step in the calculation procedure is to determine the view factor which is valid for the two surfaces under consideration. The general formula for the view factor is (1) $$\varphi _{12} = {1 \over {\pi A_1 }}\int_{A_1 } {\int_{A_2 } {{{\cos \beta _1 \cos \beta _2 } \over {s^2 }}{\rm d}A_1 \,{\rm d}A_2 } } ,$$ where s is the length of the straight line which connects two differential area elements, one on each surface (Fig. 1). β 1 and β 2 are the polar angles between the normal line of these differential elements and the connecting line. Equation (1) holds true for two arbitrary surfaces obeying Lamberts cosine law, i.e., ideal diffuse radiating surfaces. As the evaluation of Eq. (1) is elaborate and as only geometrical parameters are involved, a number of solutions of Eq. (1) exist for different groupings of surfaces. These solutions are ready for application; they are explained in the following.

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VDI Heat Atlas · K2 View Factors
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VDI Heat Atlas
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Part of
  • Dieter Vortmeyer (1_65)
  • Stephan Kabelac Send Email (2_65)
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  • 1_65 Munich, Germany
  • 2_65 Helmut-Schmidt-Universität, Universität der Bundeswehr Hamburg, Hamburg, Germany
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