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

That is, the aperture is always located at a distance of W/2 from the tower cen-
terline, regardless of the actual depth of the cavity (defined by RWCAV(1) as de-
scribed below). In multiple aperture cavities, the same receiver width and tower
height apply to all apertures (i.e., a horizontal circle can be passed through the
aperture centers). The height H is the total vertical height of the heat absorbing
unit in the cavity, as described below. A total of NUMCAV (5 4) apertures can
be specified. Single or multiple flat plate receivers with rectangular (IREC=3)
or elliptical (IREC=4) shapes are specified in an identical manner to a single or
multiple cavity receiver with rectangular or elliptical apertures, that is, using the
variables RX and RY to define plate dimensions.
In designing cavity receivers it is necessary to describe the configuration
within the cavity only in order to determine the cost, thermal losses, and flux
profiles of the receiver. All other calculations are done at the aperture. DEL-
SOL assumes the the inside of the cavity is a section of a vertical cylinder cen-
tered horizontally on the aperture as shown in Figure 11-14. The relative depth
RWCAV(1) of the heat absorbing surface inside the Ith aperture is specified as the
ratio of the radius of the cavity to the receiver radius, W/2. The bottom of the
cylindrical heat absorbing surface is chosen so as to intercept all possible images
that pass through the aperture from the farthest heliostat in the field. The height
of the heat absorbing surface is specified in one of three ways. If the default value
of the variable H is used, the heat absorbing surface height will be specified as
1.lxRY (1.1 times the aperture height). If a different value H is specified, then
that value is taken to be the actual height of the heat absorbing surface. How-
ever, the height will never be allowed to be larger than that height needed to in-
tercept all of the image that passes through the aperture from the nearest helio-
stat. Thus, the limiting values of the top and bottom of the heat absorbing sur-
face are a function of the minimum and maximum heliostat positions within the
sector of the field seen by the cavity, the aperture height, the orientation of the
aperture, the optical tower height, and the depth of the heat absorbing surface.
The equations for these limiting conditions are detailed in Section V.A-5.
If a smaller cavity heat absorbing surface height is chosen than the limit-
ing height, this will have three consequences. First, the receiver cost will be
smaller, since cost is based on heat absorber area. Second, certain receiver losses
are based on heat absorber area, and these losses will also decrease. Finally, al-
though the performance of the receiver will remain constant other than receiver
losses since performance is calculated at the aperture, some of the flux that passes
through the aperture may now be incident on uncooled parts of the interior of the
cavity (Le., the roof). The designer should verify that this internal spillage does
not cause any uncooled surfaces to fail.
1I.F. Heliostat Aiming
DELSOL has several options for aiming the heliostats at different points on
the receiver. The “smart” aiming options described below (IAUTOP#O or 5) are
generally required when trying to design flux-limited receivers. The options are
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