Environmental Engineering Reference
In-Depth Information
Fig. 12
Isotherms and
stream function for the
enclosure heated from the
top
,
Ra
10
5
,
=
ʛ
=
1
/
5and
ʵ
=
0
.
3.
a
ʓ
=
0
.
3,
10
−
5
.
ʔˈ
=
8
.
1
×
b
ʓ
=
0
.
05,
10
−
2
ʔˈ
=
1
.
5
×
Fig. 13
Average Nusselt
number for the enclosure
heated from the
top
,
ʛ
=
1
/
5and
ʵ
=
0
.
3
Fig. 14
Isotherms and
stream function for the
enclosure heated from the
top
,
Ra
10
5
,
=
ʛ
=
1
/
5and
ʓ
=
0
.
1.
a
ʵ
=
0
.
1and
10
−
6
.
b
ʔˈ
=
5
.
1
×
ʵ
=
0
.
5
and
ʔˈ
=
3
.
3
×
10
−
2
no thermal stratification is present, instead, there exist thermal boundary layers near
the upper and lower walls. Comparing the values of
in Fig.
14
a, b it is clear that
the multiple convection cells pattern flows very slowly. The remarkable difference
between the heat transfer capabilities of those flows shown in Fig.
14
is also corrob-
orated in Fig.
15
, where the Nusselt number remains constant for 10
3
ʔˈ
10
6
≤
Ra
≤
and
ʵ
=
0
.
1, i.e. the diffusion transport dominates the heat transfer process. As
ʵ
augments the heat transfer increases considerable even for Rayleigh numbers of
order 10
3
, however, the effect of
ʵ
losses relevance for large Rayleigh numbers.
Search WWH ::
Custom Search