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Table 12.1
Case test
Case
test
T
H
(C)
DT
(C)
DT
1
(C)
(Eq.
12.9
)
DT
max
(C)
(Eq.
12.11
)
Ste
Pr
Gr
mod
(Eq.
12.8
)
1.49 9 10
7
12
12
8
8
0.15
10.71
Table 12.2 Thermophysical properties
Properties T
H
= 12 C; T
av
= 6 C
Thermal conduct: k (W/m.K)
Density: q (kg/m
3
)
0.6
999.90
3.3 9 10
5
Specific heat: c
p
(J/kg.K)
4200
Latent heat: L
F
(J/kg)
Kinematic viscosity: t (m
2
/s)
1.5 9 10
-6
Thermal diffusivity: a (m
2
/s)
1.4 9 10
-7
equations are discretized on a computational domain using the hybrid differencing
scheme [
18
]. The pressure-velocity coupling is solved through the SIMPLE
algorithm. The solution of the discretized equations is obtained through the ADI
procedure. The grid defined on the computational domain is spaced irregularly to
obtain a better resolution of temperature and velocity gradients at the solid walls.
Among the types of grid tested, the 42 9 42 grid was chosen to present the results,
based on the optimal balance of precision and computational time. Table
12.1
present the test performed.
The acceleration of gravity g used was 10.0 m/s
2
. The values of the physical
properties used are described in Table
12.2
. These data have been obtained from
the work of Gebhart et al. [
19
], based on the average temperature of each tem-
perature interval considered.
12.2.3 Experimental Procedure
The experiments were performed in the rectangular test section shown in Fig.
12.2
.
The inner dimensions of the test section were: 187 mm in height, 187 mm in
width, and 200 mm in depth. The top, bottom, and back acrylic walls were 12 mm
thick. The observation window (front wall) was constructed with a pair of acrylic
sheets 12 mm thick with a 12 mm air gap between them to eliminate condensation.
The two copper sidewalls were held at constant temperatures and were 3 mm
thick. The copper surfaces were oxidized to avoid corrosion. The inner surfaces of
the test section, except the front wall and a slit of the top wall, were painted black
to minimize the light beam reflection for photographic observations. The sidewalls
were maintained at different temperatures by electrical resistances and circulating
fluids coming from thermostatically controlled reservoirs.
A schematic diagram of the experiment apparatus is shown in Fig.
12.3
. In this
figure, the copper wall is represented by (C), the acrylic wall by (A), the heat
exchanger by (E), the insulation by (I), the thermocouples by (T
i
), and the resis-
tances by (R
i
). The apparatus was insulated with styrofoam to minimize the heat
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