A User's Manual for DELSOL3 - prod.sandia.gov - Sandia National ...

point in the NMXFLX(1) array (I=l, NFLXMX) in Namelist NLFLUX
following Namelist OPT. During optimization, flux will be calculated only
at these points, rather than at every point defined in step (2).
Specify the maximum value of the flux at each point defined in step (3) in
units of watts/m2 in the FLXLIM(1) array (I=l, NFLXMX) of Namelist
NLFLUX. The peak flux limit may be different at different points to ac-
count for varying tube or metal temperatures or lifetime requirements.
For external or flat plate receivers select an appropriate automatic
“smart” aiming option (Section 1I.F). That is, heliostat aimpoints should
be spread out in some manner based on the dimensions of the receiver.
Otherwise, a flux limit could be reached on a receiver no matter how large
the receiver was, since flux and aimpoints would be localized and would
not utilize the whole receiver. For cavity receivers, where the power of
the receiver is calculated at the aperture but the flux is calculated on the
cylindrical heat absorbing surface, the flux can be reduced without signif-
icantly affecting power by increasing the depth of the receiver. This effec-
tively diffuses the flux. However, it is still recommended that a “smart”
aiming (aimpoints spread out) be used for cavity receivers, since otherwise
the depth of the cavity might need to be so large as to cause a large in-
crease in receiver costs. For any receiver, the type of aim strategy which
is used can affect the location at which peak flux occurs, and so should be
considered by the user when choosing the points in step (3).
For external or flat plate receivers, optimize the height to width ratio,
H/W, since changing the height will spread the flux differently and thus
allow the flux limits to be met. For cavity receivers, in which the flux
on the heat absorbing surface is nearly independent of the power calcu-
lated at the aperture, allow the diameter W (and hence the cavity depth
RWCAV(1) x W) to vary. This is done using the option IOPTUM=2. A
deeper cavity will have a lower peak flux level for the same power at the
aperture.
receiver size is varied the flux points remain at the same relative posi-
tion on the receiver surface, as illustrated in Figure IV-2. For external receivers,
each flux point remains at the same azimuth angle, same fraction of the height,
and on the cylinder surface, assuming it was initially on the cylinder surface. For
flat plate receivers, the flux points remain at the same fraction of the height and
same fraction of the width. For cavity receivers, the flux surface is taken as the
inside of a vertical cylinder centered horizontally on the first aperture. The dis-
placements of flux points relative to the center of the first aperture scale with the
height of the heat absorbing surface. Locations and scaling of flux points for all
receivers is discussed in detail in Section 1I.G-2.
The fluxes calculated during optimization at the NFLXMX receiver points
may be less than the maximum values allowed (FLXLIM(1)). This may be due
to one of two reasons. First, system energy costs may be lower for a lower peak
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