.
=0, Pe → Re→ . .
- :
+Pe = +Po
-λ =α - 3 ( - ):
( =- -=>Nu()=-
ρ[ + ]=- ρg+[ +.] - -
β=-1 - 1/[].
ρ t,:
β=-1
=-β =>ρ= - β (t- )
ρ[ + ]=- + β (t- )g+μ[ + ], =+ gx- .
ρ[ + ]=- + g+ +]
= -
:
ρ[ + +]=- + + [ +.]
ρ= ,:
[ + ]=- + + [ +.]
1/Pe + = + + [ .], Gr= - ( ), - .
( )
Nu=f(Re,Gr,Pe,Fo)
, , Pe=Re*Pr
Nu=f(Re,Pr,Gr)- , .. Nu=
2 : ( ) ( , ). :
. .
+ = - .
+ =0
= =0; ..
= <
= a =>
= => = = = => = , ..
= :
1) , ..
2)Pr<1,.. v<a, .
:
=a
Y=0, t= , y=
U=
Nu=0,377 =C , m=n=1/2.
Y y y
δ
δ
t x
:
= => =
:
= => =f(y)= y= y= , .. :
=μ => = y; ω=f(y). , .. ωy=const=0 ,
, :
= a =>
= = = = => , ..
= .
:
|
|
1) =f(x) , =f(x), ..
2)Pr>1;v>, .
:
y =
t= ; = ; t= ;
u=
:
Nu=0,2224 = C , m=1/2, n =1/3.
( ).
.
F V , , , , . . . .
.
.
t
dF=Vgdρ=Vg dz=-Vgβ dz
.. β=- ; ρ0 .
dt/dz>0,dF<0-
<0,dF>0
.
=- + △ +1/Re
1. - ( ):
=0=>Gr= =>Re => β△ =>ω= .. ω f(ν)
2. - ( ):
=1=>Gr=Re = β△ , .. ω=f(ν)
:
, :
Nu= C Re Gr.
c --
Nu= c --
< c - -
c - -
Nu =c , n=1/4 .
:
Nu=0,55 , 2* <GrPr<
:
Nu=0,41 , GrPr>
:
r r
t
t