Chapter 3, Problem 217P

Consider two walls. A and B, with the same surface areas and the same temperature drops across their thicknesses. The ratio of thermal conductivities is ${\text{k}}_{\text{A}}{\text{/k}}_{\text{B}}=4$ and the ratio of the valI thicknesses is ${\text{L}}_{\text{A}}{\text{/L}}_{\text{B}}=2$. The ratio of heat transfer rates through the walls, ${\text{Q}}_{\text{A}}{\text{/Q}}_{\text{B}}$ and is

(a) 0.5

(b) 1

(c) 2

(d) 4

(e) 8