CT Conduccion Ejemplos
of 13
Transcript of CT Conduccion Ejemplos
-
7/26/2019 CT Conduccion Ejemplos
1/13
EX MPLE
T
he
w
of
an
i
ndu
s
tr
i
a
l
fu
rnac
e
is c
onstruct
e
d
fr
om 0
.1
5-m-th
i
ck
fire
cl
a
y
br
i
ck
h
a
v
i
ng a
t
h
e
r
m
a
l
c
o
nd
uc
t
i
v
i
t
y o
f
l.7
W/
m
K
.
M
e
a
s
u
r
e
m
e
n
t
s m
a
d
e
d
ur
i
ng
st
e
a
d
y-
state
op
eratio
n
re
ve
a
l
ternperatures
of 400 and 150 K a
t
th
e
inn
e
r and
out
er
su
r-
faces
r
e
sp
e
ctive
ly.
W
hat
is t
he r
a
te o
f
heat
l
oss
t
hrough
a w
a
l
l that
is
0
.
5
m
by
1.2
m
o
n
a
s
id
e
?
SOLUTIO
N
K
w
S
t
e
ady-state
c
o
nd
i
t
i
on
s w
ith
p
r
esc
ri
b
e
d
w
a
ll
th
i
ckness ar
e
a
. t
herma
l
conduct
iv
ity
and surface
te
m
pe
r
a
t
ure
s.
i Wa
ll
heat loss.
S
che
ma
t
ic
:
4
00
K
1 7 W/m K
T
=
1
5
0 K
- - --
L
x
L=
5
m
Assu
m
pt
o
u
s:
l
Steady-
s
tate
c
ond
iti
o
ns
2
. One
-
di
m
e
n
sio
n
al cond
u
c
t
io
n
t
h
roug
h
the watt.
3.
Con
stant th
e
rma
l
c
o
nductivity
.
Anu
ys
s
:
Si
nc
e h
e
at t
ran
sfe
r
throug
h
the wall is
b
y
c
o
n
d
u
ctio
n
t
he
h
e
a
t
flu
x
ma
y
b
e
de
t
er
mi
n
ed
fr
om Fo
ur i
ers
l
a
w
.
Usin
g Equat
io
n
.
2
w
e
h
ave
q
=
t l
z
=
7
W
/
m
K
X
J
:
2
83
3
W
/
m
2
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EX
A
M.P
LE 1
. 2
A
n
u
n
i
nsul
a
ted stea
m
pip
e
p
ass
e
s
t
hr
ou
g
h
a room in
w
hich the air and
wa
l
l
s are
a
t
2
5
C.
The
o
u
tsi
de d
i
ame
t
er
of th
e
p
ipe
i
s
7
0 mm
, and its
s
u
rfac
e
temper
at
ur
e
and
ern is
sivi
t
y ar
e
200C and 0.8,
respec
t
iv
e
l
y
.
What ar
e
the surface
e
miss
i
ve po
wer
a
nd
i
rr
adi
a
t
i
o
n
?
I f
t
h
e
co
e
f f i
c
i
e
n
t a
s
s
o
ci
a
ted
wi
th
fre
e
c
o
n
v
e
c
ti
o
n
h
e
a
t
t
ran
s
fe
r
fr
o
m
the surface to the air is
15
W
/
m
2
K , wha
t i
s the ra
t
e of
h
ea
t
l
oss from the
s
u
rfa
ce
per
u
ni
t
l
eng
t
h o
f
p
i
pe?
SO
LU
T
IO
N
T10
1
rn:
U
nin
s
ulated
p
i
pe
o
f
pr
es
cri
b
ed
di
ameter
,
emissiv
ity, and surface tem-
perature
i
n a
ro
om wi
th
fi
x
ed wall and
a
ir
temperatures.
Fim
l
:
1.
S
urfac
e
e
mi
ss
ive
power
a
nd i
rra
d
i
a
t
ion.
2
.
Pi
p
e
h
e
at
l
o
s
s
per
unit
length,
q.
S
cl
1n11al ic:
A
i
r
-
-
T =
2
00
C
t
=
0
.
8
e
T su
,
=
2
5
C
L__
T =
2
5
C
h = 15
W /m
2
K
ts
s
11m p
ti
o 11
s:
l. S
te
ad
y
-
st
ate c
ond
it
ion
s
.
2
.
R
a
di
a
ti
o
n
e
xchan
g
e
b
e
t
ween the
pipe
an
d t
he roo
m
is
b
etween a s
m
a
ll
su
r
face
and a much
larger
en
cl
osur
e
.
3.
T
he surface
e
mi
ssiv
i
ty
and
absorpti
vi
ty
are
e
q
u
al.
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Analy
s
is:
l. T
he
s
u
rf
ace
e
m
is
s
i
ve
p
o
w
er
m
a
y
b
e
e
va
l
uated from
Equa
t
i
on
1.
5, whil
e
th
e
i
r
-
rad
i
a
ti
on
c
o
r
r
espo
n
ds
t
o G =
u
T
. Hen
ce
E
=
suT s
4
=
0
.8
(5
.
67 X
10-
8
W
/
m
2
K
4
473
K)
4
=
2270
W
/
m
2
G
=
u
Ts
r
= 5.67 X
10
-s W /m
2
K
4
(298 K)
4
= 4
4
7
W/rn
2
2
.
H
e
a
t
l
o
s
s
from th
e
pipe
is
by
c
o
nv
ec
ti
o
n to th
e
ro
o
m ai
r
an
d by
ra
diati
o
n ex-
c
h
a
n
ge
w
ith
th
e w
a
lls
.
H
e
n
ce
,
q = q c o
n v
+ q r a d
a
n
d from
Equ
a
tion
l
. l O
, with
A
=
n
D L
,
q =
h
(
nDL
)
T
s T
oo )
+
e t
; 7T
D
L
)cr T ;
Ts
r)
Th
e
he
a
t l
oss
per
u
n
i
t
l
e
ngth
of
p
i
p
e
i
s
th
en
q =
f
= 1
5
W
/
m
2
Kn
X
0
.
07 m)(2
0
0
-
25
)
C
+
0.
8
(1r X 0.
07
m) 5.
6
7
X
10
B
W/m
2
K
4
4
73
4
-
298
4
K
4
q
= 5
77
W/m +
4
21
W
/
m
=
9
98 W/m
< J
Co
m
ments:
l.
No
t
e
t
hat
tem
perature
ma
y
be
e
x
p
res
se
d
in u
n
it
s o
f
C
or K
when
e
v
alu
a
ting
t
he
t
emp
e
ra
tur
e
differen
ce
for a c
o
n
v
ec
t
io
n
or cond
u
c
t
i
on
) heat transfer ra te
.
H
ow
e
v
e
r,
temperature
mus
t
b
e
ex
p
ressed
i
n
kel
v
i
ns
(K) w
h
e
n
ev
al
uati
ng
a ra-
diati
o
n tran
sfer
rate.
2. T
h
e n
e
t ra
t
e
o
f ra
d
ia
t
i
on
heat t
ra
nsfer fro
m
th
e
pi
pe
ma
y
b
e
e
x
p
ress
e
d
as
q ; a d = 1rD E
aG
)
q c t = 1r X
0
.0
7
m 2
270
-
0
.
8
X
447) W
/
m
2
=
421 W
/
m
3. I
n
t
h
i
s
situa
t
i
on
th
e
ra
dia
ti
o
n an
d
c
o
nv
e
cti
o
n h
ea
t t
ra
ns
fe
r ra
t
e
s
are
c
o
m
p
arabl
e
be
cause T,
i
s
Jarg
e
c
o
mpared
t
o
Tsu
r
a
nd
t
he
c
o
e
f f i
ci
ent
a
ss
o
c
i
a
te
d w
it
h free
co
n
-
v
e
ct
i
on is sm
al
l. For more modera
t
e va
l
ues o
f T
s and the
l
a
rger
values o
f
h asso-
ciated wi
t
h forced c
o
nvecti
o
n, th
e
effec
t
of radia
ti
o
n
m
ay
often be
ne
g
l
ec
t
ed.
The
radiati
on h
ea
t
tra
n
sfe
r
c
o
eff i
c
i
e
n
t
m
a
y
b
e
c
o
mpu
t
ed
f ro
m
Equa
t
ion
1.
9
,
a
n
d
for t
h
e
c
o
nd
iti
o
ns
o
f t
hi
s
probl
e
m
its val
ue
i
s
h ,.
=
1
1
W/
m
2
K .
4.
T
h
i
s
ex
a
mpl
e
i
s
p
ro
vi
d
ed
a
s a
t
u
t
or
i
a
l sessi
on in
t
h
e l
nt
e
r
a
c
tiv
e
Heat Tra
n
sfer
(IHT) soft
war
e
ac
co
m
panying
y
o
ur
t
ex
t.
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7/26/2019 CT Conduccion Ejemplos
4/13
EXAMPLE 1.
6
Hum
a
n
s
are
a
b
le
to
c
ontrol
t
h
ei
r h
ea
t
p
r
oduction
ra
te and h
ea
t Jo
s
s
ra
t
e
to m
ai
nt
ai
n
a
ne
ar
l
y
constant cor
e
te
mp
e
ra
tu
re
of
T
e = 37C under
a
wide
ran
g
e
o
f
envi
r
onmen
-
t
a
l
co
ndi
t
i
o
n
s
. Thi
s
pro
c
ess
i
s c
all
e
d
th
er
m or
e
g
u
lation
.
From
the
perspe
c
t
i
ve
o
f
cal
-
c
u
l
a
tin
g
h
ea
t tr
a
n
s
fer b
e
tw
ee
n a hum
a
n
body
and it
s
su
r
roun
d
in
g
s,
w
e
fo
c
us on a
la
y
e
r
o
f
s
ki
n
a
nd far,
w
i
t
h i
t
s outer su
rfa
ce
e
xpo
se
d
to the env
i
ronmen
t a
nd i
t
s inner
surf
a
ce a
t a
tempera
t
u
r
e slightly
le
ss
t
ha
n
t
he
core
temperature,
T ;
=
35C
=
3
08
K
.
C
on
si
d
e
ra
person
w
i
th
a sk
i
n
/
fa
t
I
ayer
o
f
thickness 3 mm
a
nd effectiv
e
th
e
rm
al
condu
c
t
i
v
i
ty
k = 0.3
W
/m K.
T
he
p
e
rson
ha
s
a surface
are
a A =
1.
8
m
2
and i
s
d
res
sed i
n a
bathing
suit. T
he
emissivi
t
y
o
f t
h
e
s
ki
n is e =
0
.
9
5.
l. When the
per
son
is
i
n
s
till air
a
t T = 2
97
K, w
h
at
i
s th
e
skin
s
ur
fa
c
e
t
emp
e
r
a-
tu
r
e
a
nd
r
ate o
f
heat
l
oss to th
e
environment? Convec
t
i
o
n heat t
ra
ns
f
er to the a
i
r
i
s
ch
a
ra
c
t
erized
by
a
fre
e
co
n
v
ec
ti
o
n
c
o
c
f
fici
e
n
t
o
f
h =
2 W
/m
2
K
.
2. Wh
e
n th
e
pe
r
s
o
o
i
s
i
n w
a
t
e
r
at
T
X > =
297 K, wh
a
t i
s
the
s
k
in
s
u
rf
a
ce
te
m
pe
r
a
-
tu
r
e
a
n
d
heat loss
ra
te
?
Heat t
ra
ns
f
er to the water is charact
e
ri
z
ed
by
a
conv
ec
-
t
i
o
n c
o
e
ff ici
en
t
o
f
h
=200 W
/m
2
K
SOLUTIO
N
K 11own:
In
ne
r
su
rfa
ce
te
mp
e
r
a
tu
re
o
f a
skin/fat la
y
e
r
o
f
kn
o
wn thickn
e
ss
,
the
r
-
m
al
c
ondu
c
tivity,
e
missivity,
and
s
urface ar
ea
. Ambi
e
nt
c
ond
iti
ons.
Fiu
d : Skin
su
rfa
ce
t
emp
e
ratur
e
a
n
d
heat l
os
s rat
e for
the
person
in
a
i
r a
nd the
p
e
r
s
o
n
in
w
a
t
e
r
.
Schem
a
tici
1
1
=308
K
k
=
0
.
3
W
/
m
K
T
11
s
E= 0.
9
5
1
1
___...q ;
1
q
______.,.
1
c o n
