MIL-HDBK-1003/19
a.
Floors, ceilings, or walls that separate one control zone from
another should be excluded from the summation of terms that
contribute to the NLC. This procedure is equivalent to assuming
there is no heat transfer between zones.
b.
The total perimeter of each control zone is calculated as before by
taking the combined length of all external walls of all floors. In
this case, however, the perimeter of each floor will not necessarily
form a closed loop because walls that separate control zones (these
walls are always internal) must be excluded.
In summary, Worksheet 2 may be used to obtain an estimate of the total
NLC of any structure or, applying the above constraints, to find the
component NLC of any zone in a complex structure.
5.1.2 Calculation of the EHC and the DHC. The EHC of any direct gain
or radiant panel building with multiple thermal storage elements is given
by:
-0.22
(Am/Ac)
EHC = 45.5 [1 - e
]
(Am/Ac)
N
[SIGMA] Ai [multiplied by] si [multiplied by] EFi
(Equation 5.2)
i=1
where the indicated summation is taken over the N thermal storage elements.
The total mass surface area (Am) equals the sum of the individual surface
areas (Ai) of the mass elements in the building, or:
N
Am =
[SIGMA] Ai
(Equation 5.3)
i=1
The quantity si in equation 5.2 is a heat capacity scale factor that is
related to the material properties of element i through the relation:
si = 1.95 [SQRT [rho]ici]
(Equation 5.4)
where [rho]i and ci are the density and specific heat, respectively, of
the material in element i. The quantity EFi is the EHC thickness function
for element i and is plotted as a function of x, the dimensionless thickness
in figure 25. The dimensionless thickness of element i is:
xi = 0.362 [multiplied by] 1i [multiplied by] [SQRT [rho]ici/ki]
(Equation 5.5)
where 1i is the thickness, in feet, of element i and ki is its thermal
conductivity. In order to determine the EHC of a building, calculate xi
for each element and determine the associated values of EFi from figure
25. Then, multiply each thickness function by the heat capacity scale
factor (si) and the mass area (Ai) and sum the results. Then,
substitute the summation into equation 5.2. Mass elements not located in
direct gain zones should be included in the EHC calculation if the zones are
convectively coupled to the solar rooms. However, convectively coupled mass
is not as effective as radiatively coupled mass. Therefore, the thickness
function for convectively coupled mass elements should be multiplied by 0.4
before summing with the other contributions.
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