UFC 3-440-01
14 June 2002
Figure 3-4. Flat-Plate Collector
3-4.1.2
Array Size. The first step in the system layout is to estimate collector array
size (the actual array size cannot be determined until a specific collector is chosen for
the detailed design).
3-4.1.3
Array Tilt Angle. The collector array tilt angle is defined to be the angle
between the collector and the horizontal, with 0 degrees being horizontal and 90
degrees being vertical. The proper tilt angle is a function of the time of year when the
load occurs. For annual loads, such as service and process water heating, the widely
accepted practice is to tilt the collectors to the value of the local latitude. If the load
tends to have a seasonal variation, the tilt can be varied to favor the season. Examples
include seasonal hot water requirements, space heating, and space cooling. If the
collectors are tilted to the latitude angle plus 10 degrees, the energy output will be more
evenly distributed over the entire year, although winter losses will tend to increase, due
to lower outdoor temperatures. Tilting the array to the latitude minus 10 degrees favors
summer energy output. It is not generally recommended to tilt the array any more than
3-6
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