Chapter 15
Steady Heat Conduction
378E
Steam exiting the turbine of a steam power plant at 100
°
F is to be condensed in a large condenser
by cooling water flowing through copper tubes. For specified heat transfer coefficients, the length of the
tube required to condense steam at a rate of 400 lbm/h is to be determined.
Assumptions
1
Heat transfer is steady since there is no indication of any change with time.
2
Heat transfer
is onedimensional since there is thermal symmetry about the center line and no variation in the axial
direction.
3
Thermal properties are constant.
4
Heat transfer coefficients are constant and uniform over the
surfaces.
Properties
The thermal conductivity of copper tube is given to be
k
= 223 Btu/h
⋅
ft
⋅
°F. The heat of
vaporization of water at 100
°
F is given to be 1037 Btu/lbm.
Analysis
The individual resistances are
AD
L
L
ii
oo
==
=
=
ππ
(. /
(
.
(./
(
.
0 4 12
1
0105
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 Fall '10
 Dr.DanielArenas
 Thermodynamics, Mass, Power, Heat

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