forced convection heat transfer from a circular cylinder embedded in ...

Figure 1 : Experimental Setup (Front
View)
each air flow five different heat fluxes
were supplied to the element. By changing
the heat flux and waiting for a while to
reach to a steady state surface temperature,
all temperatures were automatically
recorded by the means of a data acquisition
system. The whole process was done for
both the clear flow and flow in the porous
medium. To compare the heat transfer rate
for each medium, Nusselt number versus
Reynolds number were plotted for all the
cases.
4. RESULTS AND DISCUSSION
Figure 2 : Experimental Setup (top view)
The air flow was supplied by the use of a
suction type wind tunnel. The inlet
temperature, the surface temperature of the
cylindrical heater, and downstream
temperature in the porous media, were
recorded through the data acquisition
system. The experiment was carried out for
three different air velocities, which were
measured using the hot wire transducer.
Pressure drop before and after the porous
bed was measures using a manometer. For
Table 1 shows different heat fluxes and
their corresponding steady state surface
temperature for various numbers. The
difference between the surface temperature
of the cylindrical heater and inlet
temperature in the case of porous media is
much lower than the case of clear fluid.
For example, in the case of Re = 1800 and
Q=15.9 W the difference between the inlet
temperature and the surface temperature is
17.2 ºc in the porous medium case and
50.1 ºc in the case of clear flow. One of the
main aims of such setup is to enhance the
heat transfer and to decrease the
temperature of the element to the lowest
degree possible. Here, we can see the
difference in the heat transfer
effectiveness. That is, the temperature of
the surface of the cylinder recorded 35.7 ºc
3