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

of the flux points along the s, axis scale with RX(1) and along the ;, axis with
RY(1) as
where RX( 1) and RY( 1) are the values of the receiver dimensions from namelist
REC, RX(l),, and RY(l),t are the values used in the iteration, and xf and yf are
the coordinates of the flux points generated by the values in namelist NLFLUX.
Generally, the peak flux occurs in the center of a flat plate receiver, unless IAU-
TOP is set to 2 or 4 (aiming at the bottom of the receiver).
For flux-limited external or flat plate receivers the use of IAUTOP=l and 2,
respectively, is strongly suggested. If all of the heliostats are aimed at the center
or bottom of the receiver, then a flux level at the peak flux point will be closely
related to a power level, so that any higher power level would exceed that flux
level. However, if the aimpoints are spread out over the receiver, then changing
the receiver size will vary the flux levels at any specific point, so that for any cho-
sen power level a specific flux limit can be reached by increasing the receiver size
appropriately. This is not a concern for cavity receivers, since the aimpoints are
always located at the aperture, so that the flux levels on the heat absorbing sur-
face can be decreased by moving that surface farther away from the aperture.
It is suggested that fluxes should not be calculated during the initial perfor-
mance run which precedes the optimization calculation. This omission will facili-
tate the process of designing a flux-limited system. Also, a single aimpoint (IAU-
TOP=O) can be used during the initial performance run to save time, since the
flux profile does not affect the system design until the optimization calculation is
done.
11. G-9. Oblique Ffux Considerations-The flux which is calculated by DEL-
SOL is assumed to be flux normal to the defined flux surface. If the flux surface
truly is smooth or if the incident flux is normal to the surface then the flux cal-
culation is correct. However, if the heat absorbing surface is composed of small
diameter tubes and the flux plane is a plane through the centerline of those tubes,
then the flux which is calculated by DELSOL will be the flux at the crown of the
tube only. Thus, if the angle of incidence of the flux is such that the flux is nor-
mal to the tube at a location other than at the crown, this location on the tube
may have a higher flux level than that recorded at the crown of the tube. This is
one reason why the aim strategy IAUTOP-2 (aimpoints spread out horizontally
and vertically) is not recommended for external cylindrical receivers. The prob-
lem is most likely to occur in cavity receivers in which the heat absorbing surface
is other than a right circular cylinder centered on the aperture.
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