MIL-HDBK-1003/19
5.1.7.3 Off-south or tilted apertures. If the orientation of the solar
aperture is not due south and vertical, the weather parameters must be
corrected according to the following equations:
a = ao[1 + Al([theta]/100) + A2([theta]/100)2
+ A3([theta]/100)2([psi]/100) + A4([psi]/100)
+ A5([psi]/100)2] ,
(Equation 5.16)
VTn/DD = (VTn/DD)o[1 + B1([theta]/100) + B2([theta]/100)2
+ B3([theta]/100)2([psi]/100) + B4([psi]/100)
+ B5([psi]100)2] ,
(Equation 5.17)
where ao and (VTn/DD)o are the south-vertical values. The coefficients,
A1 through A5 and B1 through B5, are obtained from labeled rows in the
weather tables in the column having the desired base temperature.
Interpolation between two base temperatures may be necessary. The angle
[theta] is the azimuth of a normal to the aperture with due south taken as
zero and east as positive. The angle [psi] is the tilt of the aperture
relative to a vertical position, i.e., [psi] is zero for a vertical
aperture. Equations 5.11 and 5.12 are applicable to azimuths of up to +/-60
degrees and tilts of up to 60 degrees.
5.1.8 Weather parameter worksheet. Worksheet 5 is provided to guide
the user through the process of obtaining and recording weather data needed
for design analysis. The first part of the worksheet calls for data about
the building location and the annual heating degree days. The next two
parts are parallel and provided a step by step procedure for calculating the
weather parameters needed for each of two separate passive solar heating
systems that may serve the building. If only one system is present, make
only one set of entries on the worksheet. Also, if two systems that have
the same number of glazings, the same orientation, and the same tilt are
present, only one set of entries on the worksheet is required.
Finally, the last part of the worksheet provides equations for
calculating the mixed system weather parameters in the event two non-similar
systems are present. Record the results of these calculations in the
indicated blanks.
5.1.9 Auxiliary heat consumption worksheet. Determination of the
auxiliary heat requirements is outlined on Worksheet 6. First, the scaled
solar load ratio of the system is calculated on the basis of parameters
previously recorded on Worksheets 2, 3, 4, and 5. The annual heat to load
ratio is read off the nomograph in figure 23 using the calculated value of
the scaled solar load ratio and the city parameter recorded on Worksheet 5.
Finally, the auxiliary heat required annually is obtained by multiplying the
heat to load ratio by the annual building load. Worksheet 6 guides the user
through the calculation and provides a written record of performance
analysis results.
5.2 Design refinement. The discussion presented in the following
subsections advises the user on how to modify the design just analyzed on
the worksheets if the results obtained were not satisfactory.
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