Михатулин Д.С., Чирков А.Ю. Конспект лекций по тепломассообмену
Подождите немного. Документ загружается.
., ., 2009
– 71 –
3
32
z
lg
G . (7.16)
dx
d
lg
dG
z
22
. (7.17)
.
,
rdGdxl
TT
z
ws
)(
, (7.18)
r – .
(7.17) (7.18)
dx
dg
r
TT
ws
22
)(
. (7.19)
constTTT
w
s
C
TT
gr
x
ws
)(4
42
. (7.20)
0
x
0
, -
0
C
. -
4
1
2
)(4
x
gr
TT
ws
(7.21)
, (7.10),
., ., 2009
– 72 –
4
1
32
)(4
xTT
gr
ws
. (7.22)
-
( constTT
w
s
)
:
0
1
h
x
dx
h
, (7.23)
h
– , (-
0
x
).
4
1
32
4
1
32
)(
943,0
)(43
4
hTT
gr
hTT
gr
wsws
, (7.24)
(7.22) (7.24), h-
, .
(7.27) :
1/4
Nu 0,943(GaPr )
K , (7.25)
Nu/
h
– ,
32
Ga/
gh
– ,
Pr/
– ,
)(
wsp
TTc
r
K
– -
, c
p
– .
, (7.25) -
constTTT
w
s
)( .
(7.19) q = const, . -
constTq
,
.
3
32
C
q
rg
x
(7.26)
., ., 2009
– 73 –
0
x
0
, -
= 0.
3
2
.
3
rg
qx
(7.27)
(7.10),
3
1
2
3
qx
rg
, (7.28)
3
1
2
32
3
qh
rg
. (7.29)
Re
const
q
13% ,
const
T
.
,
. . , ,
5
K
100
Pr
1
,
. K < 5 Pr <1 Pr >
100 , -
.
( ) -
, -
, ,
,
. ,
(
s
TyT
)( ), -
, , ,
-
s
TyT
)( .
14
14
.: ., ., ., .
. .: , 2003.
., ., 2009
– 74 –
-
wave
T
Nu
. (7.30)
Nu
– , -
;
8/1
3
)/)(/(
s
w
w
s
T
– ,
( s w-
, );
wave
=
(Re
/4)
0,04
– ,
;
/4Re
v
– ;
v
– (
) .
Re
-
,
, . (
x)
Tx
r
v
, (3.31)
Re
r
Th
4
Re
. (3.32)
,
Re
> 10–20, 20 < Re
< 1600 ,
Re
> 1600 .
-
.
3
4
25,025,0
)2300(Pr)Pr/(Pr024,089
4
Re
Z
sws
, (3.33)
r
Th
s
4
Re
,
r
T
Z
s
s
3/1
Ar
,
s
s
s
gh
2
3
)(
Ar ,
– -
, h – , s w, -
(T
s
T
w
).
., ., 2009
– 75 –
7.3.
,
-
. -
g-
( ) (7.7)
g
cosgg
x
. (7.34)
.os
4
(7.35)
-
, .
, -
. , << d
0
,
d
0
– ,
.
2
0
d
d
dx (7.36)
-
:
4
1
0
32
)(
725,0
d
gr
ws
. (7.37)
(7.37) , -
., ., 2009
– 76 –
25,0
)PrGa(725,0Nu K (7.38)
, (7.25) .
(7.37) (7.38) -
, (7.24) (7.25).
() -
. ,
.
. -
,
T
. -
. ,
,
, K > 5 Pr > 1. -
-
, ,
5,0
0
)/(20 gd .
,
.
7.4.
-
. -
.
, -
. , -
,
. -
, , -
. -
.
-
. -
– .
. -
,
, , -
,
.
., ., 2009
– 77 –
.
.
.
. , 5–10
, -
. -
15–40 , -
.
, () 15–30 .
,
(. ).
, . ,
. . ,
X)1"/(1RePr023,0Nu
8,04,0
, (7.39)
)/(4Re
0
dG
, G – , –
, X – .
., ., 2009
– 78 –
8.
8.1. .
, , -
, . .
-
.
,
T
s
.
«»
. -
,
-
. -
.
-
(, , -
).
. – . -
,
, -
.
. ,
, ,
,
. , -
) . -
, , , -
, .
-
-
.
: -
() T
s
, -
T
w
> T
s
. -
.
s
w
TTT
,
., ., 2009
– 79 –
() q
w
.
-
. q
w
-
T, -
. -
-
. 8.1.
, , -
. -
( AB . 8.1).
3/4
~ Tq
w
,
3/1
~
T
9
10
Ra
( -
),
4/5
~ Tq
w
,
4/1
~
T
9
10
Ra
(-
).
. 8.1.-
-
– . -
.
T
-
, (-
BC . 8.1). , -
T
= 5 °.
. -
, , -
., ., 2009
– 80 –
. -
. -
, -
, -
.
n
w
Tq ~ , n =
3–3,3.
, -
.
(
), .
. . 8.1) -
, ( F).
-
25 °
910
5
2
.
, -
( FG CD . 8.1).
«» -
. -
,
, .
.
.
-
-
.
-
q
1
( F . 8.1). ( G)
q
2
.
q
w
< q
2
. q
2
–q
1
-
: , -
. ,
q
eq
, -
q
eq
< q
w
< q
1
q
2
< q
w
< q
eq
. , -
0,1–10 q
1
/q
eq
4–6.
-
.