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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