Environmental Engineering Reference
In-Depth Information
Fig. 2
Some flow regimes, during operation, in an L-valve. These regimes depend on the intensity
of aeration
2 Gravity Flow: A Simple Model
As can be seen in Fig.
1
a the L-valve has itself an angle. If, it as was noticed by
Knowlton and Hirsan (
1978
) and Woodcock and Mason (
1987
), that a gravity granu-
lar flow there occurs. It is illustrated in Fig.
3
where three snapshots permit conclude
that a granular column (picture on the left-hand side) cannot be maintained when the
angle of the valve is smaller than
ʸ
r
. In this case
D
=
1
.
90 cm
,
w
=
1
.
25 cm and,
65
ⓦ
=
33
ⓦ
=
consequently,
57 rad.
We have estimated, from data of the snapshots in Fig.
3
, that the granular column
is reduced at a rate
ʱ
=
56
.
0
.
98 rad and
ʸ
r
=
0
.
ʽ
=
0
.
47 cm
/
s; See Fig.
4
.
ʱ
≤
ʸ
r
a gravity flow does not occurs and the granular column
must be maintained. See Fig.
4
.
In recent works on the estimation of the mass flow rate from circular holes in face
walls of bins with thick walls we have shown (Medina et al.
2013
,
2014
) that the
intensity of the flow must be proportional to
Conversely, if
(ʱ
−
ʸ
r
).
As both problems are very
Fig. 3
Snapshots of an
L-valve with
ʱ
=
0
.
98 rad
and
57 rad. This
valve does not maintain the
granular column
ʸ
=
0
.
r
Search WWH ::
Custom Search