열전달 5판 솔루션 Introduction to the Heat Transfer 5th ed Incropera

PROBLEM 1.1 KNOWN: Heat rate, q, through one-dimensional wall of area A, thickness L, thermal
conductivity k and inner temperature, T1. FIND: The outer temperature of the wall, T2. SCHEMATIC:

ASSUMPTIONS: (1) One-dimensional conduction in the x-direction, (2) Steady-state conditions, (3) Constant properties. ANALYSIS: The rate equation for conduction through the wall is given by Fourier’s law,

q cond = q x = q ′′ ? A = -k x
Solving for T2 gives

T ?T dT ? A = kA 1 2 . dx L

T2 = T1 ?

q cond L . kA

Substituting numerical values, find

T2 = 415 C -

3000W × 0.025m 0.2W / m ? K × 10m2

T2 = 415 C - 37.5 C T2 = 378 C.
COMMENTS: Note direction of heat flow and fact that T2 must be less than T1.

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PROBLEM 1.2
KNOWN: Inner surface temperature and thermal conductivity of a concrete wall. FIND: Heat loss by conduction through the wall as a function of ambient air temperatures ranging from -15 to 38°C. SCHEMATIC:

ASSUMPTIONS: (1) One-dimensional condu…(생략)