Rate of Heat Transfer for a Two-Layer System

[PotatoMerchant]

Homework Statement

Homework Equations

(unsure)

The Attempt at a Solution

Homework Statement

Homework Equations

The Attempt at a Solution

 

[Chestermiller]

It doesn't look like this has been done correctly. To begin with, the starting equation is incorrect.
For a single layer, it should read:

$$2πrLq =Q=2πkL\frac{ΔT}{Δlnr}$$

where Q is the total heat flow (watts) and q is the heat flow per unit area. This equation applies to each of the concentric layers. The problem is analogous to having two resistors in series, where ΔT is like the voltage drop across each layer and Q is the current flow through the resistors. You have to solve for the current flow, given the overall voltage drop across both layers (155 C).