(B) Summation rule for an $N$-surface enclosure: $\sum_{j=1}^N F_{ij} = 1$
(C) For a strictly flat or convex surface $i$, the self-view factor is zero ($F_{ii} = 0$)
(D) View factor depends strongly on surface temperature and emissivity
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
1. Reciprocity $A_i F_{ij} = A_j F_{ji}$ balances radiation geometry (A is true).
2. Enclosure summation conserves radiant energy: $\sum F_{ij} = 1$ (B is true).
3. Flat/convex planes cannot 'see' themselves, so $F_{ii} = 0$ (C is true).
4. View factor $F_{ij}$ is purely geometric, depending only on orientation and distance, completely independent of temperature and emissivity (D is false).