MIL-HDBK-1011/2
APPENDIX C (continued)
Section 2:
INTERIOR TEMPERATURES
2.1
Purpose
2.1.1
Internal Gain and Interior Temperature Rise. The ventilation
method and overlay in Appendix B assumes that internal gains from sun, lights,
appliances, and occupants are not high enough to increase the interior
temperature. This is usually an appropriate assumption for residential and
light commercial applications with effective sun control and roof insulation.
If internal gains are likely to be large (as in high-rise office
buildings), then it will be necessary to determine the rise in interior
temperature resulting from these high internal gains. The rise in temperature
will be a function of the rate of internal gains and the rate of heat removal.
The primary route of heat removal for this strategy will be by ventilation,
although conduction through parts of the building envelope may play a role.
2.2
Equations
2.2.1
Temperature Rise. The temperature rise can be estimated based on
the following relationship, which holds when averaged over time:
EQUATION:
heat loss by ventilation = internal heat gain
(26)
or:
EQUATION: (ACH) (Thermal Mass of Air) (Bldg. Vol) (delta T) = Q+internal, (27)
where
ACH = air changes per hour
Thermal Mass of Air = 0.018 Btu/lb/deg.F
Bldg Vol = Building Volume in ft.3-
delta T = temperature difference in deg.F
Q+internal, = Q+occupants, + lights + appliances + solar
Rearranging and restating:
delta T = Q+internal, / (ACH) (0.018) (Bldg Vol)
EQUATION:
(28)
2.2.2
Ventilation Boundary Adjustment. In the ventilation design
procedure in Section 2, the ventilation strategy boundaries are compared to
climate data on the psychrometric summary chart. These boundaries can now be
adjusted to account for the higher temperatures indoors. The boundary can be
moved to lower temperatures to represent the outdoor conditions under which
the hotter interior temperatures lie along the ventilation strategy
boundaries.
The new outdoor T+boundary, = original T+boundary, - delta T
EQUATION:
(29)
Therefore if delta T is subtracted from the T+boundary, at the 0.5
or 1.0 m/sec boundary on the original overlay, the additional percentage of
time
125
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