This preview shows page 1. Sign up to view the full content.
Chapter 4
Transient Heat Conduction
436
Large brass plates are heated in an oven. The surface temperature of the plates leaving the oven is to
be determined.
Assumptions
1
Heat conduction in the plate is onedimensional since the plate is large relative to its
thickness and there is thermal symmetry about the center plane.
3
The thermal properties of the plate are
constant.
4
The heat transfer coefficient is constant and uniform over the entire surface.
5
The Fourier
number is
τ
> 0.2 so that the oneterm approximate solutions (or the transient temperature charts) are
applicable (this assumption will be verified).
Properties
The properties of brass at room temperature are given to be
k
= 110 W/m.
°
C,
α
= 33.9
×
10
6
m
2
/s
Analysis
The Biot number for this process is
Bi
hL
k
==
°
°
=
(80
)( .
)
()
.
W/m . C
m
W/m. C
2
0015
110
0 0109
The constants
λ
1
and
A
1
corresponding to this Biot
number are, from Table 41,
11
01039
10018
..
and
A
The Fourier number is
τ
α
××
=>
−
t
L
2
6
339 10
10
90 4
0 2
(.
m / s)(
min
60 s / min)
m)
2
2
Plates
25
°
C
Furnace,
700
°
C
Therefore, the oneterm approximate solution (or the transient temperature charts) is applicable. Then the
This is the end of the preview. Sign up
to
access the rest of the document.
This note was uploaded on 01/19/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.
 Fall '10
 Dr.DanielArenas
 Thermodynamics, Mass, Heat

Click to edit the document details