Environmental Engineering Reference
In-Depth Information
2
4
3
5
1
1350
2
0
0
1
ð
3
:
48
10
5
Þ
2
0
0
W
m
¼
:
ð
8
:
5
Þ
1
56
:
31
2
0
0
This weighting matrix W
m
was chosen such that, for the aligned square heater
layout, the three performance variables inside the de-icing performance state
vector X contribute equally to the cost, resulting in a total cost of J = 3. A smaller
value of J is desirable. For the analysis discussed in Sect.
8.9.2
, ice residues in
different areas on the blade are assumed to have equal weighting in the de-icing
performance. The de-icing time t
di
is defined as the time when the total volume of
the ice residue becomes smaller than 10
-7
m
3
. In Sect.
8.9.2
, the performance cost
function J will be calculated for the other heater geometries and layouts to
quantitatively compare de-icing performance.
8.9.2 De-icing Performance Comparison for Different
Heater Layouts
In this section, the computational modeling of ice melting and de-icing performance
comparison is investigated for the different heater shapes and layouts explained at
the beginning of Sect.
8.9
. In the following simulations, distributed heaters are
placed on both upper and lower surfaces of the blade region starting from the leading
edge for the first 40 % chord length. By investigating different geometries in AN-
SYS, it is noticeable that placing heaters on both sides of the blade, while using the
same amount of total thermal power (meaning using half of the heat flux for each
individual resistor) provides a more uniform de-icing especially for those blade
geometries that have smaller cavities, or are less thermally conductive. Intuitively,
placing resistors on both upper and lower sides of the blade also provides a more
effective de-icing when ice accumulates on both sides of the blade.
For the following simulations in this section, the thickness of the resistors is
0.5 mm. Resistors are modeled as a volume, where each face has a heat flux
magnitude of 400 W/m
2
. No convection is assumed in the boundary conditions for
these simulations. By performing several simulations in ANSYS, it is observed that
these modifications expedite the simulation time while not fundamentally changing
the outcome of the de-icing performance comparison between different heater
layouts and the layout optimization. In Figs.
8.20
,
8.21
,
8.22
, and
8.23
, the ice layer
residue is shown for different heater layouts. For all of these simulations, the ice
thickness is divided into four layers (in the mesh setting) in order to accurately
capture the ice thickness variation during the melting process. Figure
8.20
shows
the ice residue at t = 200 s after switching on the resistor network. It is seen that ice
melting starts faster for circular heaters than square heaters, especially in the areas
