p19_061.pdf

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Chapter 19 - 19.61

61. We use P cond = kA ∆ T/L

∝

A/L. Comparing cases ( a )and( b ) in Figure 19-40, we have

P cond b = A b L a

A a L b

P cond a =4 P cond a .

Consequently, it would take 2 . 0min / 4=0 . 5min for the same amount of heat to be conducted through

the rods welded as shown in Fig. 19-42( b ).