A composite wall consists of two layers of different material having conductivities k1 and k2 For equal thickness of the two layers, the equivalent thermal conductivity of the slab will be:
1
k1 + k2
2
k1k2
3
\(\dfrac{2k_1 \times k_2}{k_1 + k_2}\)
4
\(\dfrac{k_1 + k_2}{k_1k_2}\)