Environmental Engineering Reference
In-Depth Information
To capture accurately the development of the buoyant plumes, an infrared camera
FLIR (ThermaCAM SC660) was employed. The infrared camera works at a range of
temperatures from 233.15 to 1773.15K and records images of size 640
480 pixels
(VGA quality). In the experiments the infrared camera was placed approximately at
a distance of 1 m, pointing towards the center of the frontal side of the sand box.
All experimental measurements were made at a room temperature of 295.15K and
at atmospheric pressure. The experimental setup is show in the sketch of Fig.
2
.
×
4 Isotherms Around the Source
The experiments presented here were designed to be allow direct comparison with
the theoretical work of Kurdyumov and Liñán (
2001
) and are divided in two parts,
where the first one is devoted to show the effects of the natural convection around a
buried heat cylinder in an air-saturated porous medium, while in the second part, the
experiments show the effects of the forced convection, as a result of the change in
position of the air stream that acts on the air saturated porous medium.
The Rayleigh number (
Ra
) and the Nusselt number (
Nu
) are defined as follows:
Ra
, and all parameters
used in the experiments are listed in Table
1
. A characteristic length and a non-
dimensional formula for the temperature were defined by Kurdyumov and Liñán
(
2001
)as:
l
h
=
K
ˁ
f
ʲ
g
(
T
w
−
T
∞
)
a
/ʱμ
f
and
Nu
=
q
/
2
ˀʻ(
T
w
−
T
∞
)
=
ʱμ
f
ʻ/
ˁ
f
g
ʲ
ʸ
=
(
−
T
∞
)/(
T
w
−
T
∞
)
K
q
and
T
, respectively. All
10
−
2
and a Nusselt
experiments were carried out at a Rayleigh number
Ra
∼
3
.
41
×
Number
Nu
∼
0
.
1590.
Ta b l e 1
General parameters
used in the experiments
Property
Va l u e
6.0E-11 m
2
Permeability (
K
)
Fluid density (Air at 293.15
ⓦ
K) (
1.2kg/m
3
ˁ
)
f
Fluid viscosity (Air at 293.15
ⓦ
K) (
μ
)
1.71E-05Pa
·
s
f
9.81m/s
2
Gravity acceleration (
g
)
Temperature of the heated cylinder (
T
w
)
353.15K
Room temperature (
T
∞
)
295.15K
Radius of the heated cylinder (
a
)
0.004795m
0.003388K
−
1
Coefficient of expansion of Air at 293K (
ʲ
)
2.45E-08m
2
/s
Sand effective thermal diffusivity (
ʱ
)
Effective conductivity (
ʻ
)
0.039W/mK
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